... don’t think if I tried for 20 years I’d be any good.
... with that being said. What would it cost to set up a shop that could profit within a year?
I'm going to be a little bit rude:
Are you already the kind of guy who already makes things? Just can't help not making things?
It takes a certain amount of that. In every trade, there are people who dream of
being a high end maker. Especially in the eyes of other people.
But they don't really dream of doing the work. day in, day out, good days and bad.
Directly to your question of profitability - I should have realized at a much younger age that nearly anything can be sold. That aside: do you have in mind cues that are either a.) more attractive than anything out there or b.) a concept that means you have a good chance of making cues that are better performance than what is out there? If not, you have to work a fairly hard slog and build a rep. Based on enough people thinking your production is better looking (at the high end: "compellingly unique") or better performing than similar options in the price range they want to afford.
I'm not in Hard Knock's class for production, but like him i am/was a carpenter/millwork/furniture maker so had all the equipment and just started making cues out of the scrap and off-cuts from my regular work. The additional cost was very low. Until you start buying wood specifically because "that might look good in a cue"
In the realm of cues, though, i just don't have much artistic talent or vision. I like simple FS cues & occasionally sell one. Which means they would pay for the effort, but not as well as other work i can do instead. So i keep it a hobby.
PS: I made my first couple shafts in the early 80's because people gave me broken sticks, or sticks they thought i could use. I had a full shop at that time except did not do turning work. So i used my buddy's Sears lathe. Some of the old makers had little more than that.
George Balabushka became a legend though he never actually "made" a complete stick. He had very little equipment, though IIUC he did have a small metal lathe. Maybe a pantograph? He understood weight and balance for those times and type of billiards games (14.1). He cut & modified Brunswick sticks to make 2 pc cues and gussied them up a bit with inlays, butt sleeves, & linen wrap. When the BBC supply dried up, he bought blanks from other makers and assembled the parts. He had both an understanding of the type stick needed for the games and times (performance) and added a subtle esthetic design improvement (appearance) that still resonates with many people. AND he did that with almost no investment + zero cnc.
At that level, it's more a matter of will, and the innate fascination to slog through the years of developing technical acumen.
People who "buy" a trade, any trade, often don't really progress enough to make their money back unless maybe they buy the maker that goes with it & act primarily as banker and marketer.