There are many frames & even home-made frames that you can look at but all frames aren't created equal. Some can't be upgraded if you decide to get a mid-arm machine. Some won't expand larger than 8 feet, 10 feet or 12 feet. Some are very wobbly--some are rock solid. Some have bumpy tracks--some are smooth as glass. Some are easy to assemble and disassemble for storage--others are better left up all the time.
Some sewing machines do not do well on a quilt frame. They can't go fast enough or sew in multiple directions.
You should ask around your home town & visit quilt shops or home users that will let you "try-out" different setups until you get more of an idea what you need/want/expect/afford. Sign up for the yahoo groups homequiltingsystems
http://groups.yahoo.com/group/homequiltingsystems/ and Machine Quilting Systems Group
http://groups.yahoo.com/group/MQSG/
Once you get your choices narrowed down to just a few frames, there are specific yahoo groups for most frames & machines.