They offer unsecure loans, not using any collateral. 

Stick with the same lender so you can cross collateralize your equity buildup without selling.2.  

Perhaps you can hypothecate the note to a lending institution, or use the notes as collateral for a bank loan?   

Very few folks at BP have had true training in Mortgage Origination, Probate, BKs, Divorce, Wraps, AITDs, CFDs, Lease Options, Title Problems, Sub2 and Land Trusts, negotiating with the seller, DOTs and Mortgages, subordination of notes, substitution of collateral, etc.

You are better off with a DSCR loan and paying a little higher rate, plus a lot less risk than using all of your net worth as collateral. 

Lot was free and clear and used as the collateral for the construction loan How did you add value to the deal?

I have a number of personal contacts, I believe, who would be interested in coming in on a loan with me, allowing me to manage all the details for a decent return (backed by collateral).

Most lenders won't do that unless you have free and clear cross collateral involved. 

@Lilly FangNo experience - what are they offering as collateral and projected returns?

We gave the buyer a 0% hard money loan collateralized by the property in under 48 hrs.