Meaning, your attorney really needs to nail all this down in a watertight agreement in order to avoid that the owner suddenly sees the gold himself.

Plaks nails it.

As for your questions -  @Tim Swierczek and @Jordan Moorhead pretty much nailed it, 1) When doing research, I use zillow, hotpads, apartments.com, craigslist, and rentometer.2)  I'd say in general SFH are actually more attractive to tenants because they get more privacy. 

I want to nail down a true number and not something inflated.

I think that @Cara Lonsdale hit the nail pretty close to the head on this one.From my experience, for a residential (1-4 unit) loan, the bank is going to use standard underwriting practices including DTI (unless they are going to portfolio the loan, in which case looking at DSCR would be the wisest choice in my opinion).However, just to clarify a bit:My experience is that they are going to do a personal DTI, not a property-only DTI (again, unless they portfolio, in which case they can do whatever they want).

@Anton Ivanov nailed it on the head. 

@Alexander Felice nailed it.

This can be as simple as having a 2x4, a saw, and some nails or screws handy, and as complex as taking the drywall or whatever off of the inside wall so you can re-do a lot of the frame.If it's just you working on it, you might think about having a piece of plywood, a couple of 2x4s, and some real long carriage bolts available. 

for the wainscoating you could use the sheets from home depot that come in 4'x8' sheets I think they are 1/8" or 3/16 thick and pretty cheap, maybe 20 bucks a sheet. cap it on the top like traditional wainscoating. for backsplash use either tile or or linoleum. the wainscoating can be put right on top with some liquid nails and finish nails and the tile could be put right on top.

@Josh Koukal - I believe @Derek Dombeck hit the nail on the head, but either you're in a hot market or you're not looking hard enough in the right places.