Not only shouldnt there be a minimum, or maximum, but I can tell you it
should not even be a topic of conversation. What happens is all the
people who soloed in short hours brag, post, tell and maybe lie. And
all the people who took a long time cringe. It does NO ONE any good.
Especially dont ask your instructor how many hours it took him to solo
and if he starts to tell you avoid the guy. Avoid him entirely if he
brags about it.

Just find a good instructor, concentrate on the tasks at hand and fly
the best you can.