Are you willing to give up some space? Although some home gyms fold to reduce their footprint (and some glideboard models can fold to store under the bed), they're usually going to stay put after assembled.
Measure your workout space. Don't try to eyeball it. Make sure you know exactly how much space you have to work with. And remember, it's not enough to account for the home gym's footprint; you also need to allow extra room for any moving parts and your body. Don't forget to measure for height, too.
How much resistance do you need? Keep in mind that as you continue lifting weights, you're going to get stronger and need even more resistance to challenge yourself. So use your current maximum as a starting point, not the end point. A weight stack of 150 pounds might be enough for an occasional exerciser, but dedicated users will want more.
How many people are going to use the gym at once? If you and a workout partner want to exercise at the same time, you'll need a gym with separate stations and separate resistance mechanisms.
Do you want to assemble it yourself? We've included estimates of how long it takes to assemble each home gym. Assign a dollar value to your time, do the math and then consider this: Would the time, money, and frustration saved be worth hiring someone else to assemble your home gym for you?