I not to sure about signing notes and stuff like that
You should probably familiarize yourself with the specifics before entering the lending niche. Here's a very watered down explanation of signing messages: In order to verify
* that the current account owner of a loan requester is not a new account owner (either through an account sale or hack), you can ask for them to
sign a message using a bitcoin address posted by them several months back. This is mainly to prevent account hackers from hacking accounts, requesting no collateral loans (or offering the account itself as collateral), and then defaulting.
* - there are cases when, during account sales, the previous owner sells the private key of a posted bitcoin address along with the account to the new account owner, so that the new account owner can sign messages with the previously posted bitcoin address.