It doesn't matter how you get your words down on paper or on tape because nobody cares. It only matters that you get them there and collect the money. You don't even have to start with a complete book. You can make workbooks, reports and pamphlets and have them printed a few at a time at Kinko's copies. Literally in a couple of hours you can have an educational product that will bring in money for years to come.
Audio tapes are easy too.
Once you have something on paper to sell in printed form, all you have to do is make minor changes and read the printed material into a microphone hooked to a tape recorder. If you can't read that well, or have a terrible voice, get someone else to read it for you. These tapes can be recorded and edited at home on your computer, or you can go to the many digital recording studios popping up all over the country. The output can be to audio tape, or you can even make your own CDs now if you want to. Packaging for educational materials is important too.