For the amp, what are your intentions? Home playing, gigging? How much room do you have and how loud do you want to go? Would just a headphone amp do?
I'm a 5-string player who started on 4-strings (there weren't many 5-strings around in the 70s). I can't see any problem with starting on a 5, and short fingers shouldn't be an issue - mine aren't exactly long. Look for second-hand instruments as well as new ones - BC marketplace, Facebook, Ebay, Gumtree, Preloved.
There's a lefties sub-forum which it might be worth asking in in case any lefties have skipped over this thread.