The 70% rule is a quick house-flip screen: multiply after-repair value by 70%, then subtract rehab. Use it to find a starting offer, then run the full Max Bid math before you bid.
(ARV x 0.70) - rehab = 70% rule starting offer
Say the after-repair value is $230,000 and rehab is $40,000. The quick screen is $230,000 x 0.70 = $161,000, then $161,000 - $40,000 = $121,000. That is not the final bid. Subtract holding costs, selling costs, financing, liens, and your safety reserve.
The 70% rule says a flipper should pay no more than 70% of after-repair value minus rehab costs. It is a fast screen, not a final offer, because holding, selling, financing, liens, and profit reserves still matter.
Use (ARV x 0.70) - rehab. If ARV is $230,000 and rehab is $40,000, the 70% rule starting offer is $121,000. Then subtract any extra reserves before bidding real money.