You might want to checkout the APQS forum at APQS.com
They have several people who belong and anyone (with or without a machine) is welcome to join. I don't have a machine yet!! am still saving.
They have a specific part of their forum that is starting/running a longarm quilting business. The posts cover everything from what to charge, how to get started, the best ways to advertise, how to increase your customer base, etc.
I recommend it for its wealth of information. Again, you don't have to own an APQS machine to join. They welcome everyone!!
Rose