70 Percent Rule for House Flipping: When It Works, When It Fails, and Safer Alternatives

Overview

If you are learning how to flip a house, the 70 percent rule usually appears early. The traditional formula is simple:

Maximum Allowable Offer (MAO) = After-Repair Value (ARV) x 70% - Repair Costs

In plain terms, the rule says you should pay no more than 70 percent of what the property will be worth after repairs, minus the rehab budget. The gap between 70 percent and 100 percent is meant to cover selling costs, financing, holding costs, overhead, surprises, and profit.

That simplicity is why the rule remains popular in house flipping for beginners. It gives you a fast way to reject overpriced deals before you spend hours building a detailed underwriting model.

But the rule is not a law of real estate. It is a rough screening tool created for a set of market conditions that may not match your project, location, financing terms, or construction risk. In a low-risk cosmetic flip with favorable financing, 70 percent may be too conservative. In a slow market with expensive debt, permit delays, or major systems work, 70 percent may be far too aggressive.

A better way to think about the rule is this: it is a first-pass filter, not your final buy decision.

For practical deal analysis, you need three layers:

• Quick screen: use a simple percentage rule to sort leads fast.
• Real underwriting: estimate repairs, carrying costs, selling expenses, and target profit.
• Stress test: ask what happens if ARV softens, repairs run over, or the timeline slips.

That approach is slower than relying on a single house flipping formula, but it is much safer. It also creates a deal process you can revisit whenever local prices, labor costs, or rates move.

How to estimate

Here is a practical way to use the 70 percent rule without letting it make the decision for you.

Step 1: Estimate ARV carefully

Your ARV is the resale value after the renovation is complete. This is the anchor for your entire analysis. If ARV is inflated, every downstream number becomes unreliable.

To estimate ARV, compare the property to recently sold homes that are:

• close to the subject property
• similar in size, layout, and lot type
• similar in age and design
• finished to the quality level you plan to deliver

The biggest mistake in fix and flip deal analysis is choosing the best sales in the neighborhood instead of the most comparable sales. A modest house with a clean investor-grade finish should not be priced against premium designer renovations unless your scope truly matches that level.

Step 2: Build a real rehab budget

Do not use a guess for repairs. Use line items. Separate the work into major buckets such as:

• demo and disposal
• framing or layout changes
• roof, siding, windows, or exterior
• HVAC, plumbing, electrical
• kitchen and bath
• flooring, drywall, paint, trim, doors
• permits and inspections
• cleanup, staging, and punch list

If you are early in the process, use a simple rehab cost estimator and then refine it with contractor feedback. For help creating cleaner scopes, see Use Generative AI to Build Accurate Rehab Estimates and Scopes of Work Fast.

Step 3: Run the classic MAO

Once you have ARV and repairs, calculate the classic rule:

Classic MAO = ARV x 70% - Repairs

This gives you a fast benchmark. It is useful because it forces discipline. If the asking price is far above this number, the deal may already be weak.

Step 4: Run an adjusted MAO

Now replace the shortcut with a more complete version:

Adjusted MAO = ARV - Selling Costs - Holding Costs - Financing Costs - Repairs - Contingency - Target Profit

This is the version that matters. It reflects your actual business model, not a generic percentage.

For many flips, these categories will include:

• Selling costs: agent fees, closing costs, concessions, staging, listing prep
• Holding costs for a flip: taxes, insurance, utilities, lawn care, HOA dues, interest, draw fees
• Financing: points, lender fees, interest reserves, extension risk, private or hard money costs
• Contingency: a reserve for unknowns, especially with older homes or system risk
• Target profit: either a fixed dollar amount or a margin that justifies the risk

At this point, the 70 percent rule stops being the answer and becomes a reference point. If your adjusted MAO is much lower than the classic MAO, the deal may be more fragile than it first appears.

Step 5: Stress-test the numbers

Before you make an offer, run three cases:

• Base case: your best reasonable estimate
• Conservative case: lower ARV, higher repairs, longer timeline
• Optimistic case: stronger resale and cleaner execution

If the deal only works in the optimistic case, it is usually not a strong flip.

Inputs and assumptions

This section is where most flippers either protect themselves or fool themselves. A usable MAO calculator is only as good as its inputs.

1. After-repair value is not the same as list price

ARV should come from sold comparable properties, not active listings alone. Active listings show competition. Closed sales show what buyers actually paid. If inventory is rising or days on market are stretching, build that softness into your pricing assumptions.

2. Repair costs need a scope, not a lump sum

When investors ask how to estimate repair costs on a house, the answer is not just “get a contractor bid.” You need enough detail to compare bids and understand what is excluded. A good budget distinguishes between:

• visible work
• likely hidden work
• code or permit upgrades
• buyer-facing finishes
• end-of-job cleanup and resale prep

Mechanical systems deserve extra caution. Roof, foundation, sewer, electrical service, drainage, and HVAC issues can turn a cosmetic flip into a full rehab quickly. For a deeper look at risk detection, see What Flippers Can Learn From Marine Stabilization Tech: Sensors for Foundation and Moisture Monitoring.

3. Financing changes the rule

The classic 70 percent rule often assumes a reasonable cost of capital and a manageable timeline. If you are using expensive short-term debt, hard money for house flipping, or layered financing, your cushion must be larger. Higher rates and fee-heavy loan structures compress your margin. The same property that works for a cash buyer may fail for a leveraged buyer.

4. Timeline risk is real

Many beginners underestimate how long projects take. Every extra week can affect interest, taxes, insurance, utilities, opportunity cost, and market exposure. Delays often come from permit reviews, contractor gaps, back-ordered materials, inspection corrections, or change orders.

If you manage multiple projects or remote jobs, tighter monitoring can reduce timeline risk. See Remote Site Monitoring: Using Cloud Analytics to Prevent Theft and Delay on Renovations.

5. Selling costs are more than agent commissions

Resale expense may include professional cleaning, landscaping touch-ups, staging, photography, buyer credits, and closing charges. If the home sits longer than expected, you may also need price reductions or additional carrying time. Your underwriting should reflect your likely exit plan, not an idealized one. If you are evaluating exit options, see FSBO, iBuyer or Full-Service Agent? How to Choose the Right Exit Model for Your Flip.

6. Profit should be intentional

One quiet flaw in many deals is that profit becomes whatever is left over. That is backwards. Decide what minimum return justifies the time, capital, and risk. Then solve backward to your offer price.

That target can be set as:

• a fixed dollar profit
• a percentage of total project cost
• a percentage of ARV
• a return on invested cash

There is no universal right answer. The point is consistency. A deal is not good because it is available. It is good because it meets your standards after conservative assumptions.

When the 70 percent rule works best

• you need to screen many leads quickly
• the property is a relatively standard single-family flip
• the rehab scope is clear and moderate
• you understand local resale comps well
• you still plan to underwrite the deal in detail before buying

When the 70 percent rule fails most often

• the house has major structural or systems uncertainty
• the market is changing quickly
• financing is expensive or complicated
• the property type is unusual, mixed-use, or highly customized
• the exit depends on optimistic pricing
• the investor treats the formula as a decision instead of a screen

For less typical properties, specialized due diligence matters more than quick rules. See When a Flip Includes a Ground-Floor Restaurant: Due Diligence for Mixed-Use Properties.

Worked examples

These examples use simple assumptions to show how the formula behaves. They are not market claims. They are decision frameworks.

Example 1: Cosmetic flip with manageable risk

Suppose a property has an estimated ARV of $300,000 and repairs of $40,000.

Classic 70 percent rule:

MAO = $300,000 x 0.70 - $40,000 = $170,000

At first glance, a purchase around $170,000 might seem workable.

Now run an adjusted model:

• ARV: $300,000
• Repairs: $40,000
• Selling costs: $20,000
• Holding and financing: $18,000
• Contingency: $8,000
• Target profit: $30,000

Adjusted MAO:

$300,000 - $20,000 - $18,000 - $40,000 - $8,000 - $30,000 = $184,000

In this case, the adjusted MAO is actually higher than the 70 percent rule result. That can happen when the rehab is straightforward, the timeline is contained, and your target profit is reasonable relative to the ARV. The classic rule may be a conservative screen here.

Example 2: Older home with systems risk and expensive debt

Now assume the same ARV of $300,000, but the property has older plumbing, dated electrical, and possible drainage issues. Repairs are estimated at $65,000, and the financing is more expensive.

Classic 70 percent rule:

MAO = $300,000 x 0.70 - $65,000 = $145,000

Now build the adjusted model:

• ARV: $300,000
• Repairs: $65,000
• Selling costs: $20,000
• Holding and financing: $28,000
• Contingency: $15,000
• Target profit: $30,000

Adjusted MAO:

$300,000 - $20,000 - $28,000 - $65,000 - $15,000 - $30,000 = $142,000

Now the classic rule and adjusted model are close. That does not mean the deal is safe. It means the rule is only barely capturing the actual risk. If the project runs longer or the sewer line fails, your margin can disappear.

Example 3: Softening resale market

Imagine your initial ARV estimate is $350,000, repairs are $50,000, and the classic formula gives you:

MAO = $350,000 x 0.70 - $50,000 = $195,000

But after closer review, you realize the strongest comp sold several months ago, newer inventory is building, and your likely resale may be closer to $335,000 than $350,000.

Revised classic MAO:

$335,000 x 0.70 - $50,000 = $184,500

A modest drop in ARV can cut your offer ceiling noticeably. This is why disciplined investors recalculate, rather than anchoring to the first attractive number they see.

A safer alternative: build your own rule

Many operators eventually stop using a fixed 70 percent rule and replace it with a market-specific buy box. For example, they might set a target based on:

• their preferred gross margin
• their real average holding time
• their financing structure
• their common repair profile
• their minimum acceptable profit

That custom formula is usually more useful than a generic national shorthand because it matches your business, crew, and market. If you want to systematize your lead flow and update assumptions faster, tools and dashboards can help. See Real-Time Market Alerts for Flippers: Build a Dexscreener-Style Dashboard for Listings and Permits.

When to recalculate

The most useful deal model is not the one you build once. It is the one you update whenever a key input changes. This is what makes the topic evergreen for real investors: the framework stays the same, but the numbers move.

Recalculate your MAO and your full deal analysis when any of the following happens:

• Comps change: new sales, price cuts, or slower listing activity affect ARV.
• Rates move: financing cost changes affect your holding margin.
• Scope expands: hidden repairs, permit requirements, or code upgrades increase rehab cost.
• Timeline slips: delays raise carrying costs and market exposure.
• Exit strategy changes: if you may rent, wholesale, list conventionally, or pursue a different buyer profile, rerun the numbers.

A simple operating checklist can keep you disciplined:

1. Estimate ARV from true comparable sales.
2. Price repairs from a written scope, not a guess.
3. Run the classic 70 percent rule as a quick screen.
4. Run an adjusted MAO with selling, holding, financing, contingency, and profit.
5. Stress-test for lower ARV, higher rehab, and longer timeline.
6. Only offer what still works under conservative assumptions.

If you are growing beyond one-off flips, revisit your assumptions across the whole business, not just a single property. A broader market thesis can help you decide whether your buy box itself needs to change. See Build an Academic-Grade Market Thesis for Scaling Your Flip Business.

The 70 percent rule still has value. It teaches discipline, speeds up lead triage, and gives new investors a starting point for thinking about margin. But it should not replace careful underwriting. In modern house flipping, the safer approach is to use the rule as a filter, then rely on a property-specific model that reflects your real costs and your actual tolerance for risk.

If you want one takeaway to keep on your desk, make it this: the best maximum allowable offer is not the highest price you can justify. It is the highest price that still leaves room for mistakes.