If you can make it work, I highly recommend a backup bike for someone who commutes everyday, particularly if you do not have an alternate mode of transportation readily available. Parts should be cheap for an early to mid 90s Giant. When you say you need brakes, do you mean new pads? In addition to new tires and brake pads, I would consider replacing the cables. Most bikes of reasonable quality are highly dependable. But when something goes wrong with one, if you have a backup you are not pressured to getting it fixed immediately before you can continue bike commuting.