Experienced investors look at dozens of properties for every one they buy, and nobody has time to build a full financial model for each listing. That's where rules of thumb come in. The two most famous — the 1% rule for rentals and the 70% rule for flips — let you sort a stack of listings into "worth analyzing" and "not even close" in seconds.
Used correctly, they save enormous time. Used as a substitute for real analysis, they'll burn you. Here's how each works and where each one breaks.
The 1% Rule: A Rental Screen
The 1% rule says a rental property is worth a closer look if:
Monthly rent ≥ 1% of all-in cost
All-in cost means purchase price plus any upfront repairs — the total it takes to get the property rent-ready. A property that costs $200,000 all-in should rent for at least $2,000 a month to pass. A $150,000 all-in property renting for $1,300 (0.87%) fails.
Why does this crude ratio work at all? Because rent-to-cost is the engine of rental cash flow. When rent is a healthy percentage of what you paid, there's room for expenses and a mortgage payment with cash flow left over. When it's thin, no amount of clever financing fixes it.
But understand what the rule is: a pass/fail screen that completely ignores expenses. It knows nothing about property taxes (which vary hugely by state), insurance costs, HOA fees, the age of the roof, or vacancy in your market. Two properties can both pass at exactly 1% while one cash-flows nicely and the other bleeds money on taxes and repairs. Passing the screen earns a property a real analysis — NOI, cap rate, cash-on-cash — not an offer. In expensive coastal markets, almost nothing passes at 1%; in some Midwest markets, plenty does. The rule sorts within a market better than it compares across them.
The 70% Rule: A Flipper's Ceiling
The 70% rule answers a different question: what's the most a flipper can pay for a distressed property?
Maximum allowable offer = (70% × ARV) − repair costs
ARV is the after repair value — what the property will be worth once renovated. Example: a house will be worth $300,000 fixed up and needs $50,000 of work. Max offer = ($300,000 × 0.70) − $50,000 = $160,000.
The magic is in the 30% you're not paying. That margin isn't all profit — it has to cover holding costs (loan interest, taxes, insurance, utilities during the project), selling costs or refinance costs at exit (commissions, closing costs), and finally your profit for months of work and risk. On our $300,000 ARV example, the 30% is $90,000: after perhaps $15,000 of holding costs and $24,000 of selling costs, roughly $50,000 remains as gross profit — before any surprises.
That's also why the 70% figure flexes. On lower-priced properties, the fixed dollar costs eat a bigger share of the margin, so many investors tighten to 65%. On high-ARV properties in fast markets, some stretch to 75%. The rule is a starting ceiling, not scripture.
Using Both Rules the Right Way
Treat these rules as the first gate in a funnel:
- Screen fast. Apply the 1% rule to rental candidates and the 70% rule to flip candidates. Discard clear failures without another minute of thought.
- Analyze survivors properly. Real expense estimates, realistic ARV from comps, actual financing terms, honest timelines.
- Let the full numbers decide. A property that squeaks past a rule of thumb can still fail the real math — and occasionally a near-miss on the screen turns out to work.
The free Shouldirefi Deal Analyzer is built for step two: once a property passes your quick screen, plug in the details and get estimated cash flow, returns, and max-offer numbers grounded in your actual assumptions rather than a one-size-fits-all percentage.
All figures are estimates for informational purposes only — not financial advice. Consult a qualified professional before making financial decisions.