Originally Posted by
ShortLegCyclist
If you live in an area where local bike shops do bike rentals, it might be worth a look to see if they are selling retired stock bikes.
They generally use bikes just a little above the price range you specified and they are maintained by the shop rather than by previous owners of variable or questionable ability, experience and motivation.
For a $500 list price Trek or Specialized or Giant hybrid you should be able to pick up a former rental bike for around $300 including tune up.
Worth looking into but inspect carefully. The bikes I have rented over the years have ranged from pretty decent to awful. If your retired rental bike was in a busy tourist destination, there is a chance the bike got years worth of wear in a season or two. And if you think about it it makes sense. A rental bike in a popular tourist area might get rented out 4 to 6 times per day, every day during the summer.