There are 2 ways of practicing martial arts for health.
One way is to practice alone, at home, by doing some solo forms (a.k.a. kata) taken from the large existing number of Okinawan or Chinese origin, with or without weapons, and/or by hitting dummies or punching bags.
This way has the advantage of minimal cost, down to zero, depending on whether you buy some training equipment and weapons or not, and you can practice without following a schedule, whenever you have time or you are in the mood.
Practicing solo is easy if you have some prior experience of doing proper training sessions in some martial art. Even without experience, if the purpose is only practicing for health and not becoming skilled in real fighting, some instructional videos can be good enough for learning how to train.
The second way is to practice with a sparring partner. Sometimes this might be possible to do with a friend, if you happen to have an appropriate space, but this is quite unlikely, so you normally have to go regularly to some martial arts training hall or club.
In this case the choice of the martial art may be determined less by some intrinsic qualities, but more by what martial art training place happens to exist close enough to your home, to avoid wasting time with transportation.
Moreover, especially when practicing for health purposes, it may be less important which is the origin of the martial art, but much more important is how competent is the instructor that happens to teach at the club that you find near you.
Unfortunately, for a beginner it is difficult to distinguish competent instructors from incompetent instructors, but after some experience the differences will become evident.
Which martial art is more appropriate depends also on the age. For someone older, a training that puts less emphasis on striking/kicking, but more on throwing and breaking falls, e.g. aikido/judo/jujutsu, is more appropriate. Also training with weapons can be appropriate for older people, as in that case the weapons are not used against humans, unless they wear protective gear.