Im 50/50 on how and when i take the 70% rule into consideration. Honestly, I think its a way for lazy investors to do half of their due diligence and bank on the 70% rule ENTIRELY. When another investor finds an easy way to evaluate multiple asset classes by one simple formula, it creates opportunity for the next.
I ask investors all the time "would you take on a fix-and-flip that had 90% Seller Financing, 0 interest for 6 months- balloon payment after 12 months, Purchase $150k, rehab $10k (cosmetic update), and ARV $200k, comps avg DOM under 10 days?" Its hard for me to believe any true investor would past this up and if they did either they do not know what they were doing or they arent investors at all.
So the 70% rule definitely has a place in flipping but it is not the ultimate determination of a deal. along side a few other considerations the 70% rule is a great tool, but like all tools they are only valuable when the are used correctly