I can only say that my wife has owned cardio equipment and if the owner used it frequently you'll probably find a lot of problems that constantly need fixing. They don't hold up well. If you can't afford fairly regular repairs in both time and money, I'd just get a gym membership -- it's probably cheaper in the long run. I'm telling you, dealing with the repair people for cardio equipment is a real pain (we've had both elliptical machines and bike, but they mostly sit unused now and if we want to and can, we go to the gym).
Do you have a bike? If you do then you can convert your own outdoor bike into an indoor exercise machine easily and inexpensively with an indoor trainer or roller. Which one is best for you depends on your preferences, goals and fitness experience.
To convert your bike to an indoor machine using a trainer, you affix your back wheel into an elevated mount and your front wheel rests on a plastic block. The bike is fully supported so you don't need to balance just pedal as you would outdoors to ride your bike in doors. Trainers offer resistance in fan, fluid or magnet varieties. Fan varieties are noisiest while magnet trainers are smooth and quiet. The most realistic road-ride feel comes from fluid trainers. Rollers are somewhat like a treadmill for the bike. You ride on top of several spinning tubes, balancing and steering just as you would outdoors.
google the item below! Not very expensive.
Bike Lane Trainer by Bike Lane Products
Be for you buy a second hand equipment check it first. make sure it still work and it will be helpful for you.