A simple promissory note might be for a lump sum repayment on a certain date. For example, let's say you lend your friend $1,000 and he agrees to repay you by December 1st. The full amount is due on that date, and there is no payment schedule involved.
Promissory notes are quite simple and can be prepared by anyone. They do not need to be prepared by a lawyer or be notarized. It isn't even particularly significant whether a promissory note is handwritten or typed and printed.
Promissory notes are contracts and contracts don't make dishonest people honest. A DIY contract is likely a mistake. You can buy a promissory note off of a site like or use a local attorney.