:)Someone I reached out to on an off market deal told me that they couldn't sell because they bought the property as a rental in the 70s and didn't want to pay the capital gains. 

Quote from @Charles Evans: There are websites that estimate market rent, but they can be off quite a bit.

The best way to develop a solid SOW is this - you start off with what you are visualizing in your head, send drawings, pictures and products that you like.

He's had two successful flips so far and after this third one he's looking to pay off the HELOC and roll the profits into his future flips.

Many details you left off though such as are you appreciation or cash-flow focused? 

Pro tip--make sure your exhaust fan in the bathroom is vented to the atmosphere--meaning out to the outside.....go out the roof or out the side of the unit or secured to an opening in a soffit vent grille off the house. 

As you mentioned, it depends on numerous factors, with pay history being a big one.

Landlords off of Gosection8, evictions?

Take the shirt off their back to pay for the damages...but not anymore.

I've largely stayed away from the "sub-to" buz word, but I have done a couple sub-to flips knowing that I only needed to hold onto them a couple months and I was prepared to pay off the notes if they were called.Sub-to for long-term hold on the other hand has me nervous.