In reply to TheDrunkenBakers:
You don't need commercial grade gym equipment for a home gym unless you are lifting serious weight. Relatively inexpensive equipment can be bought from a number of online retailers.
The following advise assumes you'd be doing squats, deadlifts, overhead press, pull ups, dips, barbell rows and bench press, as these should be your basic compound lifts. If you don't know how to do them, then the Physiotherapist in me recommends Starting Strength by Mark Ripptoe which is a very thorough if slightly bombastic breakdown of lifting technique.
My own home gym consists of: a squat rack, bench, a single 7ft Olympic barbell with cheap bumper plates, a pullup bar and finger board, and some dip bars plus some dumbells, kettlebells ez bar and bits and bobs . With this i have been able to sustain 15 years of on/ off training, and train a small group of friends as well.
Bumper plates are a little more expensive than other plates, but they let you deadlift from a better starting height so I'd go for them if you can. Or olympic size metal plates if you can't.
The absolute musts, in my oponion, are a squat rack and pull up bar/power cage, 7 foot olymoic bar and plates, and a couple of adjustable dumbells. You can do a lifetimes training with just these. Then add dips bars. Then bench.