The cost should be less than $1,000.

If you can show / prove to him that the park will be worth more because you are rebuilding the bathhouse, paving the roads and adding a playground then maybe he will feel more comfortable? 

I suspect it's probably not the same guy, but who knows. well there you go .. unless he is buying these first and then resellling might not be licensed or legal to do what he is doing anyway.

They will be on title.

But Banks only fund the very well qualified generally no way a beginner is getting bank financing unless your basically borrowing your own money. 5.

A typical amount might be 20%.

It's not gonna be a good way to learn anything.

As far as financing, I have considered  1) an FHA loan with a cosigner, and 2) going off market and approaching many owners about potentially seller financing.Any and all feedback, advice, and info on potential pitfalls would be appreciated!

If you did not and it’s unsecured debt you could be out of luck on some or all of the money as depending on his situation unsecured creditors in a bk may receive pennies on the dollar depending on what he can afford and if converted to a ch 7 you would get wiped out.Even in 2nd position he could argue the property is underwater and wipe out your lien.

Talk to a lawyer.If you get in trouble with your city you won't be able to rent it out now or later.