Unless it's to ride around the block, save your money until you have enough for a real bike. Remember when the Yugo cars became available here for around $3000? People thought, "Wow, finally I can afford to buy a new car instead of used junk." It quickly became clear however that a used car would have been much better.
Often people think, "I don't want to spend much until I find out if cycling is really for me;" so they get a department-store bike, and it's sluggish, doesn't handle well, parts don't work right, it's hard to maintain, etc., so they quickly get discouraged and hang the bike up. A couple of years later when there's a thick layer of dust on it, you say, "Hey, I haven't seen you out on the bike recently," and their response is, "Yeah, I guess cycling wasn't really for me," not realizing the problem was the equipment they bought, not bikes in general, and that nearly anyone would have come to the same conclusion given the same piece of junk.
It's like the band director at the school where my wife teaches telling about a child whose parents just got her a shiny brand-new flute, made in China, and she comes beeming through the door, and his heart sinks. And there's the parent at the door smiling to see the child so proud. How do you tell them that the poor quality is going to make that flute difficult to play, impossible to get any decent sound out of it, and that the child will soon be discouraged and want to quit and never pick up an instrument again? He says the child is much more likely to be successful if they just save up until they can afford a decent instrument.
Real road bikes, new, start at about $700-$800, and there's a good reason for it. I understand mountain bikes start slightly lower. If you buy used, you don't have to be too leery of private sellers, as there are lots of them that always want the newest thing and buy a new bike quite often even when there's nothing wrong with their old one. The going rates of used bikes are seldom much over half the new price if the bike is in good condition and still relatively new. There is a value in buying from a real bike shop however, in that they'll fit the bike to you properly and give you a reasonable amount of free follow-up service.
