Best books or resources to master seller financing?

Hello everyone, I'm currently set to close on my first two-family using a 203k at the end of October, and after going through the loan and legal process, it's crazy how expensive it can get to acquire a new property. Ever since reading Brandon Turner's book on investing with low and no money down I've always been interested in seller financing and I know it is going to integral if I'm going to buy more than one property every other year. I've tried to search as much as I can online but I've never found an indepth explanation of how the interest is paid, like if the percentage is calculated monthly like a regular mortgage, or on the lump sum. Plus the legal process for seller financing. If anyone knows of any great books or resources on seller financing I would appreciate it because I'm trying to learn as much as I can to get ready for my next property, as well as help my friends out that are also trying to get their next ones too. Thanks!!