Another classic is Landlording: A Handymanual for Scrupulous Landlords and Landladies Who Do It Themselves by Leigh Robinson, but I'm sure there are many other good ones.And of course, congratulations on your purchase of the 4-unit!

I will write a quick disclosure and say that I am relatively new but I have been doing quite a bit of reading on "Seller Financing" between classic owner finance and wraps.

Assuming she has not done any Refi's and she owns the property free and clear this is a "classic owner finance" My personal opinion would be first that you hire an attorney to draft these contracts (always when its a seller finance) the legal fees in Texas (my state) are usually between $700-$1000 for them to draft the contracts & notes for this to legally happen.

But here's a classic example that I dealt with during my private practice days. 

Mountains, relaxing etc.If you settled on the Florida Keys, you would probably be looking at a classic Florida Key West style home.

So this is the classic Return ON Capital vs.

One classic had a $180k Fed Tax Lien on it that went for around $25k & another with an EPA designated lead soil issue (complete with a do not plant vegetables in the backyard warning) & that went for around $4500.

Classic wholesaler scenario and why working with them is at your own risk.. 

Without any info that sounds like a classic BRRRROther comments are spot on.

Also, go with classic designs and colors that won't go out of style.If you're just doing parts of the house at a time, perhaps you could house hack.