I'm interested in using seller financing as an option when making deals with private sellers.  

Talking to people about REI is the best way to network and meet private lenders or partners.Talking to people with no interest in REI or who have negative opinions about it is a waste of time.Talk to the right people.It is okay to drop a hint about what you are doing if you're not sure of their opinions, but then change the subject once you know they are not worth talking to about REI.

@Dani Z.I have sent you a private message regarding your concern.Thanks!

Hamilton Zanze is a private, San Francisco-based real estate company that acquires, repositions, and operates apartment communities."

But there are other opportunities with private lending and commercial lending.

Send me a private msg.

We have a $130,000 triplex that I have a $83,000 private 5% interest only balloon mortgage on.  

Unless you have some very generous private money loans, I don't see how anyone will give you 100% of the costs to build the house (best I can find is 80% of costs).   

What's the best way to find a private investor? 

You may be in a strong position to borrow private money.