Hi Cliff - I should've been more clear, servicing loans requires a license in CA when done for others. So you should be fine for this first personal loan (regardless of sdira or personal funds).
What I mean by servicing = collecting monthly interest payments, providing necessary notices/disclosures to borrower before/during/annual, handling late payments, applying fees, and other items like adhering to state laws regarding commingling of funds and tax reporting. Again, this is not a necessary component for 1 loan at a time type of project. Servicing companies are relatively inexpensive and allow you to delegate a lot of admin & liability work.
How you charge interest is completely up to you, within reason, as there are Usury laws in each state that will require you charge a maximum rate to the borrower, max default rates, etc. Charging deferred interest is certainly not the industry norm, in my experience. Most lenders will finance up to 85-90% of the purchase price + 100% of rehab at an annual interest rate of between 9-14% depending on LTV and experience, along with a couple origination points. Interest is charged only on the disbursed amount (rehab portion is held back and does not accrue interest until drawn upon by borrower). Interest payments are due monthly, paid in arrears charged on the amount of loan used during the past month, based on either 30/360, 30/365, or actual/365 interest accrual methods. There are certainly some lenders out there that offer differed interest, but I would say they represent less than 10% of the market (ballpark guess). Clarification, I am only referring to 1st position lenders, hence the 80-90% of purchase price LTVs, most gap lenders who help borrowers fund the down payment amounts due differ their interest. From the Lenders perspective, it's obviously less risky to collect interest monthly. But if you fully trust the borrower and more importantly the equity in the underlying asset, then differed interest payments would definitely help the borrower with cash flow.
Most states consider you as just a personal investor if doing less than 10 loans per year, but this is getting into the gray area of lending laws in each state. One loan is pretty straight forward, just make sure you have a good CPA, strongly consider reaching out to an attorney (Geraci is the biggest in the industry and they know their stuff, Dennis Doss is a smaller but equally knowledgable attorney), especially if you plan to do this a few more times in the future.
Hope this clears it up.