The old Kenmores are great vintage machines that can sew through tough jobs. I can usually find them at the thrift stores for $25 or less. You want the ones that are front or side loading bobbins, not the drop-in ones. And you want one with built-in stitches, not with cams that you load into a compartment on top. If you can find one with a low-shank presser foot, they have more options for different feet than the super-high shank machines.