I suggest you be the property manager to get some experience and save money.The returns and locations C neighborhood looks fine. 

Quick Numbers..Currently Invested:  $270,000Rehab: $210,000ARV: $580,000We are offering 10% cash on cash return to any money invested. 

One is 45,000 square feet, the other 2500.I am looking for input as to whether you run: -personal credit report-business credit report-request tax returns for personal and businessAll of the above?

Your actual return on that property is pretty abysmal as a cash on cash number. 

(This year I made 40% return and 15% over 5 years so I did really well)3) My money in the market COULD keep earning above what I pay in interest?

As far as analyzing MHPs- the similarity with apartments is that you are ultimately looking at your income and expenses and what your return will be.

Would you still keep the option money from the tenant/buyer or return it?

It's important that you find good contractors, good wholesalers, and good deals in order to make your returns as big as you want.

You borrow money to invest, and let the returns from the investment pay off the debt.Saying that just because the interest rate might be lower, doesn't mean you exchange the debt. 

Again, leaning toward a safer investment over cash returns.