Hi Robert - George Coats’ book, “Smart Trust Deed Investment in California” is the classic reference guide, however its out-of-print and George has gone to the big investor forum in the sky. If you can get your hands on a good used copy via Ebay or Amazon, that’s an excellent starting place.
Lots of other stuff, but George’s book is still #1. You’re welcome to check out my personal library if you are in my area. Email me offline and I try and help you find a few other titles.
I’ve been an active hard money lender since about 1989.