Of course the ARV or market value as it relates to your CoC has allot to do with things but what you want at minimum is to earn a 6% of your money regardless how much is earns as a gross and what you pay out for borrowed money.

I have no money myself, how would I figure out what costs need to be made and percentages.

I was considering some sort of percentage of the night's rent in addition as a way to help the caretaker feel like they have a vested interested in happy guests.  

Whatever percentage you underinsure the property for is the percentage applied to the claims payout.

So a friend is offering to mortgage the house we want if we pay all costs and give him a percentage on top as well as having some equity if it appreciates. 

You may still want to budget that in, whatever that percentage is (10%)?

If your seller is not represented by an agent then he may be willing to pay your agent a small percentage to handle the transaction as a transaction broker- or, you could split a fee between you.

I'm looking for someone who will fund based on a percentage of ARV including rehab costs or maybe a partner, with cash, to go in with me 50/50.  

I'm new to Bigger Pockets and just going to jump in.My question is; If you pay a mortgage on a property, how much (as a percentage) of a return on your money (monthly payment in this case) do you expect to consider it a good investment?

What does $20k represent as a percentage below FMV?