Staker or slave botter for cash for your main.
If you want to make it mems, pins cost 12m-ish, so as long as it makes more than that per month (which it will) that's a decent way to go.
Got a friend who has 2 accounts botting gold ores at LRC and his main bots smithing. So the 2 miners supply his main. Meaning he can get 99 smith for free, well at a profit, he'll make the bars into duel rings and sell those, so its profitable smithing + crafting, 2 skills which are usually hefty money sinks.