Doing a 75% 1st mortgage and 15% heloc or heloan would likely give you better cost of funds all around.If this is an investment property, you can do 80% cash out refi using NonQM loans such as DSCR loans, but at a higher cost/rate than if you stick with 75% loan to value. 

A lot of the owner occupy loans require you to live there for at least a year, so it's not forever. 

Start by talking to a bank/loan officer to see how much you can borrow. 

And your point about a lingering HM loan makes sense.

You typically need up to two years of stable employment before a bank will loan to you.

I would get an attorney or title company involved to create your loan documents to ensure they comply with the law and cover all the aspects you need.Another method that is likely your best bet to take on investors is to create a joint venture (JV).

Also, I am guessing that due to the state of the house, it would not qualify for a conventional loan?

Quote from @Brittany Minocchi: I'm a bit farther north, but I've helped a couple of people with loans in that area - the properties seem to be working out well for them!  

(Insurance, Loans, Zoning, STR, ADU's, ??

I guess I dont understand what you asking.are you asking can a buyer cash out your equity and just take over your seller financed loan.