PMI is a set rate, you can look it up, I believe 1.75% upfront which gets added in your loan balance, plus I think .85%/yr added to your monthly payments.

Red flags are overly eager, offering to do repairs, offering advance rent payment, inability to pay FMR, deposit, LMR in advance in full, negative comments about present landlord, needing to move in less that a month. 

Guaranteed payment?

If you have good credit and a down payment, all the better.I have financed many properties both directions without problems.

From one I did years ago, most have an interest only payment for 5 years or so.......then any remaining balance gets put put on a 5-10 amortization schedule.

Sounds like a non starter.......there would be no payment history so it would sell at a Big discount and those note buyers are looking for Larger yields and Lower LTV’s than your standard refi.  

I have been managing "per cleaning visit" electronic payments to cleaning company for several AirBnB properties for a few months without issues. 

From a preforeclosure point of view - I was thinking if there is a different way to structure this , by taking over payments and if there is any advantage to that ?

Using the conservative low sale price of $500K this would net me about $170K to use as a down payment on something much larger in a more up and coming area.

I'm working on a deal where I would purchase a re-performing note (10 payments on time after workout, so far) at around 50% of UPB.