I think all strait stitch machines can be set up on a frame. You can also get a stitch regulator for them but they cost $500.
It is the cheapest way to go but it has major drawbacks. Mostly the throat area is small so most quilting pantos etc wont work. I have a few that are small enough but did not like using them.
If you do get this setup make sure to get a frame with the smallest rods you can get.
Strait stitch machines are reasonable, check out the Brother 1500 it is the same as my Baby Lock Jane.
My frame with the strait stitch cost me $1800.