You can even go down to a low res version after sculpting. It does not destroy lower subidivision versions. They are still there. So if you don't want to make a re-topology, then you can start with a low res model in ZBrush. There are lot of possibilities.

Ratchet: You will see that there are tons of nice tutorials. Even the online manual has lots of tutorials integrated and they are all fun to work through. In fact I used lots of 3d tools but the the manual and the tutorials of ZBrush are simply the best.
So I am sure you will not regret to be a ZBrush user

And the good thing is: Since you bought this tool you will appreciate it more than any warez user ever will. While a warez user will probably stop working if a problem occurs you will ask yourself and the forums how to overcome this problem since you paid for it. I am sure, you did the right thing to keep motivation on high level.
By the way: You have to register for the premium support. Then you can use their support ticket system.