The cheapest midarms (longarms aren't cheap by any stretch of the imagination) Are the Bailey, Homesteader & Voyager. Another option is to send a Juki TL98, Babylock/Brother 1500, Janome 1600 type machine to Rick at Wowquilts to have it stretched--the same guy who makes the Wow Quilter. All of these options will run you around $3,000. To get a stitch regulator--add another $500 to $700. To get a good, heavy frame to put the Voyager on, you'll need another $1,000 which includes the cost of going to the hardware store to get the pipes it uses for rails and the canvas to make your leaders.
Watch ebay, craigslist and join some of the yahoo machine quilting groups and you may get a bargain. I got my Voyager and Proflex frame so cheap off ebay that I'm embarrassed to tell how much. It feels like I robbed someone. It didn't have a very good description but after 3 years of drooling over other folks midarms, I knew what I was looking for.
I started quilting using a 9" domestic machine that I would take off & on the B-Line Studio frame I bought new. I used it for 1 year that way then added a PC Quilter and Max Throat (also purchased new). I love my PC Quilter! (They quit making Max but you can still find used ones) Max allowed me to quilt up to 14" in one pass but it's finicky and not as smooth moving as a midarm would be so I kept dreaming & learning until the Voyager showed up. That happened right before the AQS Quilt Show in Paducah so I didn't have any extra to buy goodies but I had a good time and learned about new things to dream about & drool over--LOL!