Buying fitness equipment is not always the easiest task. Finding the right piece for your home gym often means heading into unchartered territory. Everyday Health [1] offers some great tips on making smart fitness buys. 
Here are highlights [2]:
- Keep what you like to do in mind. If you hate taking the stairs, a stair-stepper isn't going to change your habits. A treadmill might be a better option.
- Because many types of equipment require a sizable outlay of money, look for the one that offers the most complete workout. If you're setting up a home gym, a good strategy is to devote the bulk of your budget to a good quality cardiovascular machine. Supplement that with less expensive strength training pieces, such as dumbbells and resistance bands.
- Measure the space where you plan to install the machine and carry the dimensions with you when you shop. Stair steppers, for example, are quite tall.
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- Bring a healthy skepticism about performance claims with you when you consider equipment. For example, most aerobic equipment will burn 400–600 calories an hour, not the more than 1,300 calories that some manufacturers claim. And no device is going to produce "perfect abs" in just three minutes a day.
- Keep in mind that it's impossible to burn fat from just one part of the body. Don't be swayed by emphatic testimonials or dramatic before-and-after pictures.
- Take a test drive before you buy. This means spending some real time working out on the machine in proper exercise clothes and shoes. Don't make your decision on the basis of a few seconds of use while still in your street clothes. Also, reputable dealers will often allow you to try out the machine for 30 days and return it for a full refund if you're not satisfied.
Source [3]