Having to store the equipment, or worse, having to disassemble it, will be a deterrent. Also, exercise equipment can be noisy and bother people nearby. Expect to spend at least a few hundred dollars or be disappointed. Nonmotorized treadmills, for example, are inexpensive but may be clunky to use. But spending several thousand dollars is not necessary.
Some machines cost more because they measure heart rate, calories burned, time elapsed, etc.
These are nice features, but not absolutely necessary for most people. Programmable machines that can automatically adjust the workload may not be worth the price, since manual controls, if accessible, work just as well. You can walk, jog, or run on a treadmill. Walking stresses the joints least, but jogging and running will burn more calories per minute. The treadmill surface can be hard.