Let's say I want to purchase another single home for 500k which 174k remaining still in 25% sales price of the property.

Still, the question remains.  

The remaining 31 pads just have water and electric but need septic added. 

Then if you have any remaining entitlement eligibility, you could use that to buy your next place that you would live in.

Is there a way we can notarize a document in which he is obliged to give me the remaining profit.

If it is attached to the property is becomes part of the parcel and would remain during a foreclosure The mobile home if not converted to real property would belong to the owner and he may remove it much like a car   

If I did the unsecured loan for 6 months at 9% the below is what the cash flow situation would look like:Loan Pmt: $470Taxes: $102.35Insurance: $85Vacancy: $60 (750 x 8%)Repairs: $37.50 (750 x 5%)CAPEX: $56.25 (750 x 7.5%)Rental License: $40 (yearly)Property Manager: $45 (750 x 6%)Rental Income: $750By doing this I would net (-$108.16) or (-71.41) if rented for $800 for the fist 6 months assuming I can get someone in there within a month to pay all the remaining bills.

Could turn a 3bd 2ba into 4br 2ba or 3bd+Den 2ba and sacrifice and move into the addition and rent out the remaining spaces to cover rent + extra.Multis 1-4: Same as SFR with one unit and you can rent out the other units for a premium.They key is to find an undervalued property, due diligence, be skeptical, and be able to acquire and/or add sweat equity to increase value/rents.

@Ryan CorcoranI have heard about people using commercial loans to purchase multifamily and putting only 5-10% down, getting 75% from the bank, and having the owner carry a second for the remaining amount.

The existing house will remain on the property.