Welcome!
Since you have arthritis, ask a couple of questions about the height adjustment flexibility of the frame and the various options for loading a quilt.
I have a used system I picked up used for an excellent price, and am very glad to have. But I would really like all the poles to 'flip' out and/or up to a comfortable height for attaching the quilt. Like you, I have arthritis and sometimes the bending over is just too much. Pinning the backing, batting and top on the frame can be painful, too! There are other devices - like Red Snappers (I never tried them) - to help you easily attach the back, bat and top, which might be helpful to you.
Also think about your height in relation to the minimum and maximum height of the frame plus the sewing machine. Bending or stretching for long periods of time is not fun!
If your arms and hands are affected by your RA, you might want to consider a computerized quilting system. The computerized systems read a pattern that you load into the software for the long arm, and then push the sewing machine around on a carriage to quilt out your pattern.
See if one of the long armers that you take your quilts to will let you try their set up. If a local quilt shop has a long arm set up and gives lessons on how to use it and/or rents time on it to customers, take advantage of that. That alone will be very helpful when you make a decision about which machine and frame to buy.
Good luck with your purchase.
I have a HQ16 - midarm - and it works wonderfully. I've had no problems with it since bought it used and am very happy with it. So I can recommend the Handiquilter line of long arms.