i do machine quilting for part of my income. many quilters charge different amounts, i believe that location has alot to do with charges. some people charge by the square inch, some by the project, some by the hour...it depends on you...first you have to buy a machine (not cheap...it is an investment, as large as buying a car) then you have to learn to use it, then you have to PRACTICE, PRACTICE, PRACTICE. some people find that they enjoy doing panto's, some like to do free-motion-free hand quilting; everyone has their own style. and their own learning curve...some people take hold, jump right in and start out doing quite well, others practice, practice practice and never feel as if they are doing good enough to work on other people's quilts. and time....well, if you like making quilts you may just find you spend all of your time quilting other peoples quilts and never seem to have any time to make one yourself, or you do manage to get one made once in awhile, but it stays folded up under your quilting table because someone else's is always loaded up.
before even thinking about such a commitment you need to start with trying out as many machines as you can, take lessons, demo machines and get in some practice. the only reason i have my machine is because the person who originally bought it thought they would set it up, load up a quilt and be making money hand over fist...well with their second quilt reality sunk in, it takes time it takes practice, it takes commitment...and it takes up a huge amount of space. you can not just buy a machine set it up and be a great quilter. anhd along with experience and practice you need to do a market survey...are there 40 really good quilters already in your town? or is there no one for 100 miles doing it? it takes time to build a customer base. if you do decide to jump in and give it a try it will take some time to build up enough return customers to reach the point where you actually are making any money. i think it took me about 4 years to reach the point where i believe the machine has been paid for and then i was finally making money with it