I'd suggest that you consider a "real" career, with any martial arts career being something you do on the side, at least at the start. That way, you can pay your bills, meet your obligations, and generally support yourself until the day comes that your martial arts business will do so.
I'd also suggest that you get the appropriate business training, so that you can effectively run a school. Some people manage to do so with no real preparation, and others more or less buy a franchise from someone (or in some other way get the business as a package)... but I feel pretty safe in saying that most schools try to get by without having the proper business tools, and as a result, lots go under quickly -- and others end up in situations that hurt the business and the martial arts instruction (like bad leases, improper insurance coverage, branching into areas that require licenses that they lack -- think daycare disguised as a "before & after school program, and lots of other things).
And -- if one day, your "hobby" or "side business" takes off, and you can make a living at it, fantastic!