Oops, I missed this on my first read through.

Like the other guy said - craigslist, or someone who wants to sell you their road bike from the 80's or something is about your only bet. Around me there are shops that accept donated bikes and fix them up - maybe that's the way to go. Or maybe you can find an old used "mountain bike" (the kind when mountain bikes didn't have suspension, just had fat tires).

If you want something new, solid, reliable and new for minimum money, your best bet would be to buy a "hybrid" from a bike shop - $400-$500. Decent entry level road bikes are priced more at the $700-$950 mark (new), but even there sometimes they come with some crappy wheels that might not survive lots of pothole hits.

When I was younger, $900 would buy you a good, solid, midlevel road bike. $1500 would buy you something top end. Also, $5 would get you into a movie in a theater during regular (non-matinee) hours. But prices have gone up, sadly.

If you buy a $200 bike from walmart or target, whether it's a road bike or mountain bike is unlikely to matter - it's probably not going to last that long. Sometimes they do - but it's a crap shoot. And I've read threads where someone has bought one, replaced one or two inexpensive parts, tuned it up themselves, and gotten it to work. But I'm just warning you - in the forums at least, they have a reputation for only being built to go about 100 or 200 miles before they break.