Idk, f2p is a hell zone when it comes to botting.. gosh I feel sorry for legit players there..
Anyways back to the topic,
Mining is possible (Rune mysteries takes 5min to do, its a 5 stage quest and with home port and the teleport your offered during the quest, you can do this on 5 chars+ an hour)
Woodcutting, though it is a bit crowded.
Karamaja lobs/swordfish, should be possible, dno how much it would make.
That would be the only ways I'm aware of, haven't bothered to farm much in f2p, its just too crowded imo..
Good luck!