Make sure the Mac you get has a high density drive (sometimes called a SuperDrive). The Macs without SuperDrives are the 128K, 512K, 512Ke, Plus, SE (unless it is marked "FDHD" or "SuperDrive"), and original II. All other beige desktop Macs will include a SuperDrive. (Do not confuse this SuperDrive with the DVD drive used in modern Macs; the name was simply recycled many years later).

Check the classifieds on this forum; a lot of people are selling old Macs right now.