Mona Lisa -
Lots of good advice on this thread. I bought a very nice traded-in Pfaff 1475 for either $300 or $400 a few years ago. Since then I have found 4 vintage machines that are awesome performers for $80, $20, $15, and $45. The $20 was a Featherweight. Just keep an eye on thrift stores, Craigslist, the classifieds in your local paper, and estate and yard sales. Consider the adventure of the search.
I hope you enjoy the search and find a great machine.
Darren