My question:If I were to seller finance and then raise private capital for the rehab, how would I pay back the lender loan other than chewing through income from the rentals since I would already be paying the seller on the finance?

Did you have the rental income coming during the first year you owned or it was vacant? 

Now, I know you were asking about rental income...and that you can find in the comps too. 

The best source may be to call active listings as well.

If you want the income lending/lending funds would probably be a great option, but there is rarely any equity appreciation.

Seller financing is a great way for the seller to avoid a lump sum capital gains tax, and still make steady/expected income on a property even after they sell it. 

House hack potential of adding two separate rental income sources while living in the main house.

This means your monthly rental income should be at least 1% of the property's purchase price.

I wanted to obtain a rental to gain passive income.

Even though we have a history of rental income at that property and a 2yr lease in place.