Well, I know for a fact that most REI's will rent gear.

so start looking at some of our gear lists, some of the discussion on the site, decide what you want to try, and my
suggestion if there is an REI near you is to rent the backpack
for the first few times out. If you then get the rest of your
gear sorted, then buy a backpack.
Any fool can be uncomfortable...
My 3 season gear list
Winter list.
Browse my pictures