I had absolutely no expertise in longarm quilting and was very much the beginner as a quilter. I did some research on machines..bought a Gammill 26" Classic + in 2004 and haven't looked back. I was white knuckle for the first few months but soon learned it was a sewing machine..albeit a really big one. I started doing customer quilts after about 3 months..(brave souls they were to trust that I'd not make a disaster of their quilts). I worked hard to learn, read, took classes, practiced and practiced some more. I still love my job, work out of my home (huge cost savings there) and continue to practice (a lot of it by drawing designs I want to perfect over and over again)
I totally love the look on a clients face when she/he sees their quilt after I've completed the quilting. Would I do it again..absolutely.
BUT and it's a big but, if you are considering buying a machine to do the quilting on your own quilts..you can pay a longarm quilter for doing a lot of your quilts when you consider the price of these high end machines. On the other hand, you may want to quilt for others as well as yourself. Do the research, how many other longarm quilters in your area, how many quilt guilds in your area where you may pick up new clients, can you afford to travel to major Machine quilting shows to take classes, are there fabric shops in your area (potential clients there)?
If I had it to do it again, I would not hesitate to buy a well kept used machine, go to those shows and test drive the machines. I was lucky, I got a great machine, have built a good business and after 7 yrs I'm looking forward to another 7 yrs.
Good luck, sorry to be so wordy.