@Dorian F. I am a firm believer that you make your money when you buy. It's important to structure your deal and your plan correctly out of the gate. For any long-term strategy, this should account for natural ups and downs in market.
For example, I do only buy and hold rentals, no flips. When I buy, I do so with a 75% LTV (sometimes 80%, but rarely) on the purchase price. Since I do buy/hold, my analysis is centered more around rents, cash flow, and principal pay down. ARV vs. rehab cost is secondary but the ARV generally falls above total expenses.
Now, here is where I differ from a lot of other investors, I don't do a refinance to get the LTV % back up to 75 (or 80) against the ARV, I keep it as is from the purchase price. This generally means I'll end with well over 25% equity which drives higher than "normal" cash flow... which for me, can ebb and flow with market fluctuations.
I think a lot of people will disagree with my approach on the last part b/c I keep a high amount of money tied up in equity, but It works for my long-term vs. short-term objectives.