Don't buy the cheapest machine on the market. It will give you hours of frustration instead of pleasure.
My mother hated to sew, back in the days when women were expected to sew housedresses and children's playclothes, so she *did* buy the cheapest machine she could find. It wouldn't keep the right tension, no matter what you did. She had it serviced, got the timing adjusted, but if you sewed more than 6 inches, it was back to making loops on either the top or bottom.