I do this!
http://www.sign2speak.com
In my opinion, the absolute best organization to work with/through is
www.sign2me.com. You can go there and see who offers sessions in your area. There are solid requirements to become a presenter, as opposed to some organizations that you just sign up, pay for a kit of some sort and then go out to teach. That's why I chose this organization, though. THey are also very intent on using ASL and not home signs.
Now, in my experience as a busy mom of two, it takes awhile to build up this business. You have to network and get in with the right people and places. But once your name is out there, you'll get busier. I am just now (two years into it) to the point where I don't feel like I need to discount my prices to get business. I've been consistently busy and jus decided to invest in some pricey advertising. Now I can honestly assess requests, asking myself "is this worth my time at $xx/hour?" I may have gotten to this point sooner if I hadn't had a baby in the middle of it and a baby that turned out to need mommy a lot! Or if I had had more babysitting so I could have more availability.
So yes, I think it's a good idea, esp. if you have outlets and ideas on how to get started!