If you're a mage you can make runes depending on your vocation. For Master Sorcerers the greatest amount of money I got was from Magic Walls before the NPC's because you could find mwalls on market being around 30gps-50gps more than the Edron NPC which was the only one who sold em. I would then, invest in having rings and softs and sit for hours making runes to the point I would do 200k a day selling mwalls, either for buying from the NPC and sell em or just making them which was way better. But these runes are not a great source of money anymore. They're still profitable but I switch to do SD's because there's always people buying or selling and they go for a little bit more that the ones you get from the store In a good day I do around 1000-1300 sds and I wait till I have 20k and sell them all in a bunch or just every time I catch a good market price range moment.
As for Elder Druids I find more profitable than anything doing paralise runes and avalanche runes, and same, selling them via the market, I also do uhs but idk how those work since I keep them for myself. But the best source of money is from the Paralise I sell.
You can also profit while being AFK if you're an RP 150+ by conjuring arrows and selling them for at least 10k a bunch of 100 depending on the server, and you get to do 100 every 10 minutes. Also there's always people on the market buying arrows.
And last but not least, I've found a lot of profit by getting tips from imbuing weapons. My main char has all the imbues and I sit in DP all day or at my friend's house doing imbue for people and most times they tip me with 20k per imbue or so. I figure if you do this constantly and change the tips for actually charging ppl and offering the service (ofc if you have a good reputation) then this means you can do good money out of this too.