From what I've seen in my time here, the most profitable botfarm is a safe botfarm.
As others said, I'd contact KMJT if I were you, and ask him for some advice, he can even help you setup a botting vps for you.
What I mean by a safe botfarm is a method that doesn't get you banned like other methods.
A lot of botfarms get banned more often than they can make accounts and rebuild so it's in your interest to create your own, non-saturated, private method.
That's pretty much the only way you're going to make a profit in the long run if you don't plan on investing, or not investing a lot.