You'll probably want to try and familiarize yourself with the game first, then gradually get into botting, and eventually, a bot farm.
Months ago, Sorc Garden bot farms where the craze, people where getting 400k/hr which is the equivalent of 40c an hour back then on dozens of accounts at once. Since then however, such revenue rates have subsided.
You could probably start out with some F2P bots to get a feel of how maintaining them is like. Some common ones include Ash pick-upers, vial fillers, yew cutting (in f2p), crafting. You may get 50k/hr with this, not a lot, however it'll give you a feel for how maintaining bots work, once you've grasped it then you can take it to the next level.