As Maniac said, think long and hard before you turn a hobby into a business. It often turns a fun, enjoyable activity into, well, work.
As far as pricing goes, you can google 'long arm quilting services' to get rates from different providers as a starting point. This will also give you an idea of other services they charge for: squaring a quilt, fixing borders, seaming backing, pressing, etc.
Pricing varies by geographic location. Some places, you can get an overall meander for $0.01 per square inch, some places the lowest is $0.015 or $0.02. If you go to your LQS or ask at a guild meeting you should be able to get info for local quilters.
I worked with a local quilter and quickly decided that it wasn't for me: wonky tops, threads all over, pet hair, wavy borders etc. Plus they want it yesterday. I'm very careful as I piece my tops, I don't need to deal with other folks' problems.