The most important rule is to have the cash flow of the new property be able to pay all its expenses, mortgage, AND the line of credit back.

A good deal for a retail buyer is something they can pay for which has most of the amenities and location they want.

Quote from @Cameron Moore: Exactly. 15 years ago, I noticed an increase in owners using insurance to pay for a replacement roof, usually to sweeten the pot during a sale.

The flipper pays 12.5% interest to the lender, and I receive 10% of that.

because I was paying my bird-dogs vs having them pay me and just promise how someday, maybe just maybe they will bring the grand-slam of a deal and then I will be paying them oh-so much $$$$$ Seriously, from those buying into this I gotta understand how your mind works, no insult meant, I am genuinely intrigued and baffled because if it's a good deal you can go to any number of investors and get $, not a one will charge you for the opportunity to present them deal. 

How much do they want you to to pay, to pay off one of the mortgages (or both of their existing mortgages)? 

But now 50% are not paying.

IE securing them paying tax's insurance etc etc. 

If I sell one house per year, it will pay for itself.

Quote from @Ricardo Lemus: For a newer investor, a good investment is a property that pays for all expenses with some cash left over.