According to the conditions you mentioned, my advice is to buy an Elliptical instead of a treadmill.
Please note that both of these are training tools and maybe they will make you want to practice in the beginning, but the important thing is your will to continue for how long. Results are not achieved with short-term training, so you should train for a long time.
Elliptical, or space skiing, puts less pressure on the joints and makes the exercise more pleasant, and as a result, attracts people to go for this type of exercise.
Good luck
