Wanting to build a garage (Need advice)

Ditto on the 12' ceiling.

My buddy has a 14' tall roof and his lift requires 12' ceiling.

My garage has 9' ceiling therefore I need a shorty lift and have to reinforce my 4" thick floors if I put a lift in there.

Yeah do the floors 6" thick, rhibar reinforced, get the lift pad stencils so you can bury allthread where the posts will sit.