You didn't cause the problem which is a major factor in the premium impact.

Timely payments are one of the largest factors in a credit score and if he hasn't had late payments since then, his score would continuously improve.

The most major factor in most markets is affordability.

is there a particular formula that takes all manner of factors, (employment growth, corporation development news, barrier to entry, rental rates, wage growth, etc) into account and spits out an "invest in city X" answer?

This may not seem like a big deal, but it is something that you will need to nail down and factor into your analysis.

I do agree with the sentiments from others regarding the experience factor.

We use these factors in this order of importance (feel free to create your own):1) Tenant pool credit score2) Location => Neighborhood3) Property condition & amenitiesClasses are not defined for the SFR industry and are relative to the area.

MAYBE they adjust that up or down 10% depending on outside factors but they’re not checking the assessed value. 

That’s a factor in getting rehab upfront.

Its really going to come down to multiple factors, including your personal situation/strategy but it appears you are definitely thinking about things in exactly the right way.I'd say since it doesn't seem to be an "urgent" need - I'd advise talking to some lenders and since the rate environment is still moving quite a bit, settle on a interest rate / points combo that is "your number" and when market rates move down to that point - have the lender contact you and get ready to go, and just wait until that occurs