Bike Commuting

As I'm preparing for the eventual buying of a house and move to said house, I'm also preparing to give up my bus route. College Town (where Public U. is located) has a fairly decent public transportation system for taking people to the university (this is limited only to and from the university and only in certain regions of town). Alas, the houses we are looking at are not within this area. This is because (1) there are only a few houses in this area-- most dwellings are apartment complexes, (2) there are a high concentration of loud undergrads in this area, and (3) all houses in this area are well out of our price range. So, being the moderate liberal that I am, I'm looking for alternate means of transportation to the lab.

So far I've come up with a few ways of minimizing my impact on the environment/gas prices. The least environmental of these is to car pool in with Dr. Man. The most would be to just walk in to work. I think the most reasonable of these would be to bike at least one way. The one way contingency is because I do not feel comfortable riding my bike by myself after dark (whether or not this is a reasonable safety concern I do not know). If it's after dark, then I'll catch a ride with Dr. Man home.

However, there is one snag in my brilliant, yet modest, plan. I do not own a bike. I've thought about buying one at Target/Walmart for about $60, but Marie (who happens to be very into biking) has cautioned me against such a move. She claims that the weight of the bike matters a lot and the positioning of the bike. The bikes that she recommends are in the $300-600 range.* That strikes me as a lot of money to spend on this, especially since (as one might assume from my lack of a bike) I don't ride a bike now. What if I decide that I hate riding a bike and walking would be better? Or some other unforeseen problem (like laziness) that causes me to not want to ride a bike? I'm willing to save up for a more expensive bike, but I don't want to sink a lot of money into something untried.

So, right now I'm stuck. I usually try to avoid soliciting advice from my readers (as that seems rather selfish-- I'm already making you read my words and now I want you to act as Dear Abby?). But as I said, I'm stuck. So, if there's anyone out there with tips for me with commuter biking-- help!

ETA: *I've been checking craigslist, but I've yet to find anything. Besides I don't know a good bike if I see it on there... sigh