You can get a good DVD-+RW Drive for about $30.
Or a CD Burner for about $20
Or just a CD drive for like nothing if you cannibalize an older computer.
If you really want to get fancy, you could get one of these
A simple CD drive would be all you need for installing an OS (or DVD drive, depending on what media the OS comes on.) There is really no point in getting a cheap, minimal drive because they are so cheap now. ($30 for a DVD burner)