If I were planning to consult with a tax adviser and attorney to work through this process, I assume that would be sufficient to mitigate the risk. 

FHA has an added guideline on 3 and 4 units called self-sustainability or self-sufficiency (i always mix them up). basically it means that the rental income from the units have to fully sustain the PITIMI, or else its a no-go.

I don’t coach in those things because I don’t feel my experience is sufficient in those area yet.

People who live in high-crime locations and have sufficient income will leave.

As a result, crime rates increase and people with sufficient income leave the area.

It's hard to find a sufficiently cash flowing deal on Zillow or the MLS with how fast deals come and go right now.

If you and your wife both have stable and sufficient income to support your living expenses, then I'd use that investing capital to do the BRRRR strategy. 

Is it sufficient to determine what the all-in price including offer and rehab costs would need to be to make a deal work?

I think a S-Corp is too much unless you have sufficient income to justify and it still doesn't make sense if your income is passive.You might each want to have your own entity that comes together to do the deal..Ultimately, its whatever works for your group...That being said, I would strongly advise for you to look at the various other threads we've had on BP. 

With sufficient income, you get the bank's attention and qualify for loans.