A note is a promissory note, a promise to pay a debt, evidence of a debt.
A lot of people think a mortgage is a debt but it’s a security device. So is a deed of trust.
To be a legal note, all you need is to identify the parties, who is paying the debt and who is receiving the payments. You don’t have to identify why, you just have to identify the agreed terms. You need to state the amount and the payments and the payment frequency,
Many people think you have to give interest on a promissory note. No you do not.
Many people think you need financial or physical security for a promissory note. There are unsecured promissory notes with no security.
In the real estate investing space we help motivate sellers sell their properties and get most of their equity out, but we create notes that benefit us regarding the interest and payments.
Many times in a seller of financing situation we will try to not pay any interest for 5 years or more. Our feeling is that we want the seller to get every dime of equity out of their property but not create interest for them too.