Suggestions:
- Make an account on FurAffinity. There's a lot more interest in furry stuff there.
- Decide what payment options you'll accept. Most artists use Paypal, but snail mail is also a [less reliable] option, among other things.
- Figure out what you want to charge. Look around at other artists' prices, think about how much you need/want to make, etc. Making prices cheaper can be a good way to get started off because more people are likely to buy, then you could raise them later if demand increases.
- Advertise. Post on furry forums, post journals/notes on DA or FA, ask your friends to advertise for you too... whatever you can do to get the word out.
- Draw a lot! The more art you submit to art sites like DA, the more people will see your work, and the greater chance someone will come along who wants something from you.
- Get commissions done quickly, and stay on top of communicating with your clients. Clients can often come back for another drawing if they like working with you; if they have a bad experience, they won't return and could also tell other people to stay away from you. Do not want!
Good luck.