I would suggest that you look for something like a Singer or a Jones or Pfaff or Brother, but make sure it's got a metal body. The plastic ones end up falling apart they go eggy coloured and crumble
while the older sixties and early seventies machines are still in really good nick and modern enough to easily get spares 'and' they're considered old fashioned enough to buy cheaply
All you really need is a machine that will sew forward, backwards and do a zigzag stitch. Anything else for basic sturdy sewing really isn't needed.
There are a lot of much more expensive machines out there, as well as really, really good older ones, but the cheap end of modern is pretty clunkery and the really, really good older ones (hand or treadle) are awkward to store in modern homes.
See if you can find one with it's case still in good condition. I've got two and they're brilliant
cheers,
Toddy