For instance, other real estate investors may be willing to do a seller-financed deal because they would view the benefits of the note is included in their investment portfolio.

What benefit do you think you are going to get? 

Put NOI in the numerator and divide by Annual Debt Service, must be greater than 1.25x.Costs for repairs really depend on how much asbestos you have (you might not have any) and cost to replace K&T wiring (depends if the wiring is accessible from a drop ceiling, in an exposed basement, open attic, or behind plaster walls that will require some cutting and patching. 

Give them the benefit of the doubt and take responsibility for the window. 

One benefit (of many) is the unlimited use of the calculators.

I've written numerous posts on Bigger pockets, check it my reply here:  first time home buyer, FHA, multi-unit. 

To that point,my wife's car loan is a 4.25 percent interest rate so it would be easiest to pay off, but the benefits of paying it off would also be significantly lower.

That doesn't mean you won't be able to benefit from the RTO payments and the remaining balance once you own the park. 

New to investing, and I have a complicated life with finances, here's a quick back ground, I have a corporation, and so I don't make much money personally due to divorce complications and children, and my corporation has been utilizing the tax benefits, so I am sorta shooting myself in the foot twice I already know, but I have bigger plans to make my life better just need options.  

Bravo to you for building what you have and reaping the benefits!