Your local bike store (LBS) can be an expensive solution in search of problems, if you follow my meaning.

Let me clarify: a few years ago I bought a mid-1980's vintage mountain bike which I intended to use for basically the same purpose the OP described. It cost me $20 at a garage sale. It had been a few years since I had been on a bike, so though I once knew how to change a tire, etc., I had long since forgotten. I don't know why, but it never really occurred to me to look on YouTube, ask on <a href="http://www.bikeforums.net/forumdisplay.php/10-Bicycle-Mechanics">Bikeforums</a>, and so forth. Long story short, my LBS charged me nearly $250 for a bunch of easy stuff I could have/should have done for myself: new tires, new tubes, new brake shoes, a little lubrication. In hindsight, it was my fault; basically I approached this like an idiot with an open wallet. It would have been worse, but I stopped them from doing a bunch of other stuff which was unnecessary and even more expensive (changing cables, new freewheel, blah blah blah). I still have that bike, and nearly 1500 miles later, I have a clearer understanding of what it needs and does not need. It didn't need all the expensive stuff they told me it needed.

If you're going to commute on this bike, you will need to remember/relearn a few things: changing tubes/tires, lubrication, cleaning, etc.

So while I agree the folks at the LBS **can** be a great resource, it's not always true. Before you go throwing money at this, do your homework a little. Post some pictures of the bike, either here or at Bikeforums, and include some closeups of drivetrain components: front and rear derailleurs, brakes, chain, rear cassette/freewheel, tires, and so forth. Include some specifications: are you the original owner? How many miles on the bike? etc.

Where are you located? Are there any bike co-ops around you? Here in SoCal, there are many. They are <a href="http://www.bikeforums.net/showthread.php/577108-List-of-bike-co-ops-collectives-and-bike-kitchens">not hard to find</a>. I took my vintage mountain bike to <a href="http://www.thebicycletree.org/">one</a> and for $20 got some really good help.

Yes, some bikes probably require the extensive (and expensive) servicing mentioned by other responders. But I have a few bikes I've gotten used and I've put some miles on them, and in every case but one, the only things I did were new tires, new tubes, a little lubrication, new seat, new brake pads/shoes, and some cleaning. For the record, my vintage mountain bike (1986) is still running on the original grease in the hubs and bottom bracket, but it was evidently not ridden much by the prior owner(s).