Miniatures painting in small apartment

Hey all, short-time lurker and first-time poster.

My brother lives in a small apartment with two other people and wants to get more into it. problem, as. you might have guessed, is that there isn't a lot of real estate. stuff can't stay out in one place and it has become an issue.

So the question: do y'all have a list of things that you feel are absolutely essential but can still fit in a small box that can be easily taken out and put up again? What do you use and what would you leave out? What do you store everything in?

He's used paint pens in the past and likes them fine, but wants to be able to do more fine detail.

Also - priming. how do you do it in a small space in an urban area? tips or tricks to avoid suffocation (indoors)/arrest for graffiti (outdoors)?

ty