Searching out a decent used bike for cheap is not necessarily everyone's idea of a good time. I understand that. But you don't need to buy the first one you see, or any of them. And no matter what you find, you are going to have to decide whether you're going to do all the work on it yourself or have a bike shop do it. And you have to face the fact that many bike shops will be less than thrilled at working on an older bike.

Buying a cheap new bike is a little different. You can find one right away; no time is wasted trying to find the right one. Then you have to decide whether you're going to do all the work on it yourself or have a bike shop do it. And you have to face the fact that no bike shop will be thrilled at working on a really cheap bike.

As for reliability, it's a gamble either way, and if you don't know about bikes you're going to have to learn a lot either way. A good old bike may have worn out parts that are hard to replace; and cheap new one is built entirely of junk parts that require constant attention and probably have to be replaced pretty soon. In general, I think you're better off going with a used bike.