I’d have a pro do an inspection and estimate You are basically asking a crystal ball question.... no one can predict the exact future of the roof..... it may last you years with no issue or it may leak in the dead of winter and cost you 3x as much .... no one really know.

- If you're going to do this you'll have to develop a metric to predict the next crash.  

If you ask renters and potential home buyers in Sacramento, they'll tell you prices are too high and many predict a crash.

Get a full understanding of the surrounding properties and what they charge for rentals to help better predict your cap rate. 

If rates go up as I'm sure they will (demotivating buyers)... but at the same time there are more buyers in the market it seems hard to predict or even estimate if buyers will actually be there to purchase a flipped property for a decent profit within the next couple years, especially if that property is purchased in today's market! 

So you naturally can get a little bit of accidental (but predictable) blind leading the blind.

How do you run the numbers when you have to try and predict the market in 2+ years?

Over the Life of the Loan, the interest rate (APR) will never be higher than five (5) percentage points (5.0%) above the initial Loan rate o f_____________ %.I understand and agree that a refinancing of the outstanding loan balance with you is subject to your credit approval and current credit standards and policies which you reserve the right to change without notice at any time.It cannot be predicted at this time whether or not you will exercise the option; however, it will generally be to your advantage to exercise the option if an increase in ANNUAL PERCENTAGE RATE has occurred or is anticipated, which would jeopardize your earnings and your ability to meet your financial obligations.

Even with experience, as you point out, there are variables when the re-sale is  3-6 months out that can't be predicted.  

As for it making sense, we, in insurance, can only use past claims to predict future claims.