What are obstacles that could prevent you
from keeping a job

There are many. (im going to try to be specific as possbile) You need a good resume. Witch means good handwriting. You need to be smart in that subject. witch might require college. and college is Quite expensive. If your overweight. they may not hire you even if you are experienced. Because people are very judgemental. (Hope this helped!)

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.