I'd agree on Singer and Husqvarna. Buying second hand was fine for me - I've got 2 2nd user Singer machines - and actually, the older one is the better of the two. It has solid metal rather than nylon gears on the main drive, and whilst noisier in operation, has far more torque, which is what you need when sewing thick things like denim at slow speed.

Look for a machine with zig-zag capability (useful in all sorts of places) and maybe overlock, rather than just basic straight stitch capability.

Best regards