I would focus on advancing your 3d skills in general first. It’s not the program that you use, it’s the experience with 3d concepts and getting accustomed to a program’s toolset. I’d suggest starting with blender’s sculpt mode and doing a lot of sculpt work with a free program before dropping cash on a specialized sculpting app.
On note of making money - you’ll have to be fairly good with whatever app you’re using, and find which type of work you excel at… then the fun part - finding clients. If you have no solid clients and no experience with zbrush (or any other similar app, i.e. blender), then it’s going to take a while before you’re “good enough” to make money at it.
It’s just like sports, and “going pro”. Don’t worry about getting endorsements and sponsors, just have fun doing / playing that sport, and if you are dedicated enough eventually you’ll get sponsor offers by word of mouth, rather than seeking them out and “biting off more than you can chew.” Just as with blender, use it, learn it, love it, as a hobby, and have FUN… the “sponsors” will come in time.
that’s my 2 cents :RocknRoll: