Is RedBubble any good for artists and sellers and how does it work?

RedBubble is a Print-on-Demand service. How it works is that you upload your designs for a product (shirt, iphone case, etc.), and post it for sale for others to buy. You set a royalty amount that you get paid everytime they print a product with one of your design on it. I've never used RedBubble, but I've used similar POD services. You generally have to wait a certain time period (usually around a month) until you're given the money credit that you've earned. This is done just in case a customer decides to cancel an order or return something. When the time period has cleared, you can get paid, usually by PayPal or checks.

POD sites are generally not good for making an income that you can live off of. But they can give you some nice pocket change, if you're willing to put the work into it. Put effort into the designs you produce. And advertise your designs. Relying on RedBubble alone to market your work won't get you as many sales.