I'd say the #1 best money maker is merchanting, but you would need atleast 40m to start with (to buy the cheapest partyhat first, buy it at night (least players on), sell afternoon when prices go up 5-10m and 150k+ people are playing, 5-10m per day at occasions 2nd would be kalphite queen hunting, only do if you are lvl 100+ this can easily beat merchanting only if you get lucky (which is a good chance actually since the queen drops chain 1 out of 100 kills) you can go with no more than 2 people, soloing it will make you lose money (since you lose about 50k per trip if you don't get a chain, but again i am talking about if your luck is average) and takes 2-3 trips to actually get a random drop (-1m to 20m per day) 3rd and most easiest is runecrafting, once you reach lvl 44 craft nats using the general store method, or if you've done the quest, the gnome glider method, if you reach lvl 91 it would beat everything else even with no luck having to decide how much gp you earn 400-800k per hour