My question is can I legally keep their security deposit?

Ben, I own a lending company that offers loans for investors.

Many land purchases require cash, not loans and most people don't know that...or if you can finance it, maybe a bank will loan 50% of the price...and seems like so many people don't have that 50% to put down. 

Does anybody know if my father can prove his income to a lender when I try applying for an FHA loan instead of my income?

You should not calculate that in your review honestly.Curious if you have the cash for that debt why not just pay it off as the interest is probably burning a big hole in your pocketTotally get what you're saying and I plan to pay off my CC debt regardless of this deal; however, they are also asking me to pay off a big chunk of my car loan now which is why the number increased after the rate hike. 

I manage 325 units currently, and there are quite a few scammers out there that use this even to secure an apartment and then never pay.

Mainly due to aggressive underwriting as apartment prices shot up and they started getting floating interest loans to make the numbers work.

I'm planning to pursue a conventional loan with 10% down payment.

Would be happy to connect and get a loan summary over to you today.

Yep, there a plenty of ways to acquire real estate without getting a bank loan or paying all cash!