+1

Two basic stitches are all you really need - straight and simple zig-zag (a necessity for stretchy material). -a button-hole stitch is very useful too, btw.

More expensive and newer machines have dozens more different stiches, but in 30 years of sewing, I have used almost none of them. Some of the newer machines also have automatic threading which is a nice feature, but you can get along without it. I have sewn three-piece dress suits, shirts, pants, bicycle clothing, moccasins, leatherwork of all kinds, repairs of all kinds - all using very simple stitches.

You can get some very nice sewing machines at thrift stores now for about $10 to $20. If you are lucky, you can get one with a sewing table too. You can hardly go wrong with that. In fact, my opinion is that the older machines are more heavy duty and are better at sewing a larger range of materials. Look for machines with more steel and less plastic. For example, the old sewing machines from the 1950's and 1960's will punch right through a piece of leather or a thick stack of canvas, but some of the later machines groan and choke when put to that kind of task.

You mentioned that you buy off of Craigslist. If so, just ask the owner what condition the machine is in - ask if there is anything wrong. Describe what kind of sewing you plan to do and ask if they think the machine will be appropriate. Most folks are honest and helpful and will give you a straight answer.