Deposits from the tenant.Security deposits from the tenant in residential dwelling units shall be deposited in a trust account with a licensed and federally insured depository institution lawfully doing business in this State or the landlord may, at his option, furnish a bond from an insurance company licensed to do business in North Carolina.

And being in California, you really should be using licensed companies for everything.

We are considering becoming a private lender with them and I am doing some background research on him and his companies and wondering if anyone has done any deals with them.

A professional trustee such as Exeter Trust Company is the way to go if you want it done right, imo. 

They want them all jammed in large apartment complexes, run by large companies, in concentrated areas, away from them.

The specialist I recommend you have is an attorney to properly draft the documents and a title company to facilitate the deal.

Before the great recession, as a 22-year-old that knew nothing, I did a few flips and ran my own property management company.

As mentioned have an attorney or title company draft the note and mortgage.

Plumbing company says its the only way to resolve the issue I have.

I hired an IRA-approved valuation company to value that note at that time.