I fully agree with DogHouseMom. LQS/sewing machine dealers often have used machines that have been fully checked and oiled, etc. They may also offer time payments. Many quilters do 'trade up' when able.
Also, you might ask at your quilting group. You never know who has a good machine they are willing to sell.
While I haven't looked, there might be something on the QB.
Good luck.
ali