How does the loan process work without proof of income and what percent down is required? 

Right now the only thing I can think of is to sell and I definitely don't want to do that.

Although I'm currently in the process of becoming an agent, becoming a broker prior to escrow closing would be impossible.

@Irving GonzalezUsually you have 4 options for leveraging a property to help pay for another: selling, cash-out refinance, HELOC, or a home equity loan.

I believe he is working on completing a roll up of the RV parks in the hopes of selling it to P/E down the road. 

First I'll look at comps that are in the same neighborhood and see what they are selling for.

Also, if I am a homeowner, I can't think of the benefit of selling "sub to". 

It sounds like you’re selling for $500k after closing costs?

I am getting ready to purchase my first rental property, and am going through the process of what I want my leases to look like.

you have to put the work in with the remodel either way but if they're high-end condos you can sell them each for more than the property as a whole and make more in one transaction than you would on a cashflowing rental