The 70% Rule in House Flipping: A Screening Tool, Not Your Max Bid

You're standing at a tax-deed auction with $50,000 in capital. A property comes up that needs work. You pull out your phone, do the math: purchase price × 0.70 = your max bid. The formula feels bulletproof. But here's the reality: that 70% rule just kept you from the worst deals. It didn't tell you what to actually pay for this one.

The 70% rule is real estate's most borrowed shortcut. It's also the most misused. Understanding what it protects against—and where it fails—separates investors who survive their first deal from those who learn the hard way.

What the 70% Rule Actually Is

The rule is simple: offer no more than 70% of the after-repair value (ARV) of a property, minus your estimated repair costs. The math looks like this: (ARV × 0.70) − Repairs = Max Offer. If a property will be worth $200,000 after you fix it, and repairs cost $30,000, the rule says: don't bid above (200,000 × 0.70) − 30,000 = $110,000.

The 30% buffer is meant to cover your holding costs, carrying costs, realtor commissions, closing costs, unexpected repairs, and profit. It's a margin of safety built into the formula itself.

What It Protects You Against

• Emotional overbidding: The rule removes ego from the equation. You can't chase a property if the math says no.
• Repair estimate creep: Most flips go over budget. The 70% rule assumes they will and leaves room for it.
• Market timing risk: If the market softens before you sell, that 30% buffer absorbs some of the loss.
• Quick exit failures: If you can't sell as fast as planned, carrying costs pile up. The margin helps.
• Dead-simple filtering: At an auction or in a hot market, the rule helps you say 'no' fast to obvious overprices.

In short: the 70% rule is a guard rail. It keeps you out of the ditch. That's valuable. But a guard rail is not a map.

Where the 70% Rule Breaks Down

The 70% rule assumes every deal needs the same margin. But real estate doesn't work that way. A low-rehab property in a strong market may support a higher bid. A complex flip in a slow area might need more buffer. The rule treats them the same.

• ARV estimates are guesses: Comparable sales data is public, but your ARV depends on condition, timing, and buyer pool. Off by $20,000 and your 'safe' bid is now underwater.
• Repair costs are rarely final: You don't know the roof, foundation, or electrical until you're inside. Even with inspections, surprises happen.
• Holding periods vary wildly: A 3-month flip and a 12-month hold have different carrying-cost reality. The 70% rule doesn't distinguish.
• 30% profit isn't always right: In a hot market with low interest rates, you may accept tighter margins. In a slow market, you need more.
• It ignores local context: A rural tax-deed property has different exit velocity than an urban rental renovation. The rule doesn't account for that.

Most critically: the 70% rule assumes you know your ARV with confidence. If you don't, the rule is only as good as your guess.

The Real Danger: Using It as Your Max Bid

This is where the rule trips up investors. They treat it as law, not as a starting point. They assume that if the math hits the 70% number, the deal is safe. But the rule is a screening tool. It says 'this deal is worth analyzing further'—not 'this deal is a yes.'

A real max bid comes from your specific situation: your capital, your holding costs, your risk tolerance, your exit timeline, your local market strength, and your repair accuracy. Your max bid might be 75% of ARV if repairs are clear-cut and you have $50,000 in reserves. Or it might be 60% if you're stretched thin or the ARV is soft. The 70% rule can't know your life.

Worse, many investors reverse-engineer the rule. They find a property they like, calculate what 70% of ARV minus repairs would be, and then set that as their offer without testing it against their own numbers. That's not underwriting. That's wishful math.

How to Use It Right

• Use it to reject obvious deals fast: If a property fails the 70% rule, walk away. It's unlikely to work.
• Use it as a floor, not a ceiling: If a deal hits 70%, that's when real analysis starts, not where it ends.
• Adjust for your margin: Are your repair estimates reliable? Are you fast at closing deals? Do you have capital for surprises? Let that shape your actual max bid.
• Stress-test your ARV: Check three comparable sales, not one. What if the market drops 5%? What if you need to drop price 10% to sell fast?
• Know your holding costs: Calculate exactly what it costs you to carry a property per month (interest, taxes, insurance, utilities). Use that in your bid.
• Separate the rule from the calculation: The 70% rule gets you in the room. Your personal underwriting gets you to offer.

When You Might Bend (or Break) the Rule

There are times when paying more than 70% of ARV makes sense. A sub-$50,000 property might support a higher bid because commissions and closing costs hit you harder as a percentage. A property with clear, low-cost repairs (fresh paint, landscaping) in a hot market might justify 75% or even higher, if ARV is solid. A rental hold with cash flow might not need the same exit margin as a flip.

But bending the rule requires that you've done the math yourself first. You know your ARV. You know your costs. You know your market. And you've calculated what you can afford to pay while still hitting your return target. The 70% rule didn't tell you that answer—you did.

The Bottom Line

The 70% rule is a screening shortcut, not a substitute for real underwriting. It's a fast 'no' for bad deals and a starting point for good ones. But it can't replace the work of knowing your numbers, your market, your costs, and your capital position. Use it to filter. Use your own analysis to decide. That's how you stay standing when others walk away from bad deals—or worse, get buried by them.