Running a card room is a lot harder than it appears. You only need to look at the chip guide for states with legal card rooms to see how many closed places were once around.
http://www.chipguide.com/
A card room is a cut throat business. You are always trying to recruit customers from other venues and they are trying to poach your players. Success is often fleeting, the "new place" is attractive if for no other reason it is new.
Running a card room in a competitive market is surprisingly capital intensive. You will likely need more money, staff and experience than might be anticipated. The lack of prior experience will be an on-going problem. New operators don't know what they don't know. I have doubts you will granted a license to operate a card room, if that is what you are considering.
Perhaps one might think it would be different running an illegal game out of an apartment. Put a couple of tables out, hot stamp a few thousand chips get a crate of cards and a wall full of illegal booze sold without a license. Can't cost more than $5,000 to get set up - you'll make that back the first night.
The fact the original post exists offers insight. It is good that someone is asking before doing. But I hope it comes across that this is potentially a really bad idea. More so if the idea is to become part of the criminal underground. Perhaps it is just me thinking of myself, but I have the impression old men make bad novice thugs.
My advice? Go get a job in a legitimate card room, if you can. Let someone else train you on their nickel. Learn if you really want to do this. It is harder and more tedious than you think. Don't try to learn the business on your own, with your own capital at risk.
Consider the implication of joining the ranks of organized crime. Sure, you'll just be a "small fry" barely getting your beak wet. Is that a good place for some old retired guy? Some of the other members of the criminal underground don't play well with others.
Let's just not do this so quickly -=- DrStrange