Do you have any goals in regards to riding? Putting around, canyon carving, racing maybe?
as far as your questions…
1) Depends on what kind of riding you do… maintenance for me is pretty pricey since I race my bike as well as commute and canyon carve.
2) Depends on your level of what becomes uncomfortable for you. I’ve heard of people your height refer to the ninja 205 as being cramped as well as others saying it’s fine. Sit on as many bikes as possible to get a feel of the riding position… make sure you have someone hold the bike upright for you while you do this as that will give you a better feel compared to sitting on something resting on a side stand.