It's a whole different ballgame if you join one that's actually making a profit and doesn't need someone else's cash. Get in as early as you can, if you like the idea and can see it's got longevity.
Startups rely on fast growth. If you have a very narrow market or your end goal is $200k/yr in profit, you are by definition not a startup.
If you're actually a startup, you should not have any profit in the beginning. You should be pumping that money back into the company and seeking external funding in order to pour gasoline on the fire.
There's nothing wrong with having a business instead of a startup (personally I prefer the bootstrapped business route) but to say that it's a startup is not accurate.
Only in the Hacker News / Silicon Valley echo chamber.