Do you know of any universities that have a degree program in real estate? I don't. But they should. If you have a knack for investing in real estate and have had some notable success, you can pass on your investment know-how to newbies!
Many people today are intimidated by cooking, and might welcome some one-on-one instruction. If you're a great cook, have a particular specialty, and especially if you cook on the frugal side, there may be a willing market.
If there's one skill in life that everyone has a universal need for, it's financial knowledge. If you are lucky enough to be a whiz at finances, or especially if you work in the financial industry, you hold a wealth of information that can be a real asset to everyone.
Many adults who have never played an instrument want to learn, but would do better with a private instructor who will provide close training at a more relaxed pace. If you play an instrument, this could be your niche.