I'd suggest getting the galaxy steel for $395 including shipping from bikesdirect: http://bikesdirect.com/products/mercier/galaxy.htm

It is a steel road bike with wide range of gears, a place to mount a rear rack, and integrated shifting/braking.

If you can afford to go a little over the $400 mark, the Kilo WT5 for $479 has internal braking and shifting for lower maintenance. It also has space for adding a rear rack: http://bikesdirect.com/products/mercier/kilott_wt5.htm

If you can afford to go up in price a bit more, the Tourist is perhaps the most versatile bike that bikesdirect offers for $599: http://bikesdirect.com/products/windsor/tourist.htm It comes with a rack and has room to add front and rear fenders.

I own the Tourist. I don't work for bikesdirect. They do offer NEW quality bikes at prices that a local bike shop likely can't match. The only problem with buying used, is that you have to search and be lucky to snap up a bike in the size you need. Also, ebay is overpriced for used bikes. You can be lucky to find deals on craigslist, but you really have to be lucky.