I'd look at the closing docs for something related to the pro-ration of expenses etc and see if you have anything there that could be a clause you point to for them to cover those payments. 

You might get these days 60% leverage so you'll likely need 40% down payment plus reserves and the financial institutions will want you to keep those capital reserves in their institution.If you are a new investor, there's a couple of opportunities to get started. 

I know that when I’m buying a loan, I’m buying the future payments at some price.

If it’s verbal, they’ll need to document any prior communication or payment records to establish the relationship.If the PM is completely unresponsive, they may want to send a formal written demand for communication and payments via certified mail.

I had a chat with them on the phone as i was curious about the funding.. but came to the conclusion that the down payment ( the client made to buy) was probably what they paid for the property and the seller carry back note was the profit.. and then the seller carry back note is sold to yet another investor.. who is investing for coupon money.   

Financing: I'm confident I can put $10,000 down as a down payment within the next year.

It's just that I've already established good working relationships with some people in Jacksonville that I know are reliable.

What you spent on the land/lots can go towards your down payment and, if you've owned the land for more than 6 months, you can use the value of the property toward the cash injection requirement.

The interest only payments aren’t getting any cheaper.

Section 8 is has the benefit of guaranteed payments by the government.