I applied to 10! haha
I had a bachelor's, so I had taken most of the courses required by all the schools. If you're trying to do your pre-reqs in 2 years, it'd be very difficult to satisfy the requirements of that many schools. A lot of them are not very lenient with substituting courses.
They all pretty much require the same core courses, but then there's random credits like economics, psych, etc. some require physics II, some A&P, etc.
I would make sure to take main courses required by most schools and the few random extra courses required by your top choices. Then if you get in somehwere else, you could prob take the extra classes they need inthe spring (if you apply early) or over the summer (if they allow it).