Hi everyone!
I have been selling my 3d models on online markets that deal with this type of content for a couple of years now, and it has been quite profitable. One of them has just recently opened up to stock images (photos, renders, illustrations). I thought, "OK, why not", and uploaded some high resolution renders for sale, and the sales started coming in almost immediately! If anyone wants to take a look at the site, and maybe sign up, please use my affiliate link: [link]
There are no contracts to sign, and you can start or stop at any time. Payouts are made promptly on the 1st of every month and there is no payout limit (you don't have to earn up to a targetted amount before they pay you).