Purely anecdotal, but we are purchasing a home from family with seller financing. Due to the relationship, we agreed on a 3% down payment and the IRS minimum interest rate for a family loan (in our case, 2.47%). The loan has a 30year term. We are also getting the home for below retail. Although we don’t anticipate any issues, we had a proper agreement of sale, mortgage and note, and we are closing with a title company (so there was a title search and we have title insurance) and will be using a loan servicing company to avoid any confusion about payments, balances due and taxes. In other words, it’s possible to get private money at a favorable rate from friends/family or other lenders. You can treat it like any other lender and have the same structure in place for managing the loan. It helps to understand your lender’s motivation. If it’s purely a for-profit venture for the seller, then yes, rates may be higher. Our seller was interested in cash flow on a monthly basis and wasn’t concerned about overall profit margin as much. We would have had no issue getting conventional financing, but in this case it made no sense since we could get the money at such a low rate for an extended term.
TL;DR - with private money, almost everything is negotiable, which is a good enough reason to pursue it.