As someone who has worked for MSPs serving small and mid sized businesses, I would not do this. They aren't going to pay you monthly, they have very little free cash for invisible things like this. There's just no value add here. If anything goes wrong, you're on the hook. You'll need insurance for sure. They may not pay you. You'll need a lawyer on retainer. If their printer stops working, you'll have to prove it wasn't you and you're not getting paid for that time.

Stay far far away from small businesses unless you want it to be your full time job.