How to make money in RS

Mine your own ess with your runescape account.Mine however much you want to reach your Runecrafting level goal or get the amount of airs you want to get and sell. (Calculate how much money you will get from the ess you have once you make airs out of all of it.)
Buy an air talisman (you have to have done Rune Mysteries quest to make air runes, let alone any kind of runes.) This is easy. Also, if you want to do this faster, buy a tiara. (This will make you an air tiara. This is the point of an air tiara: All you have to do is put the air tiara on and you can enter the altar faster and save extra space for rune essence.) To make an air tiara: Bring an air talisman and a tiara into the air altar. Use the tiara with the altar, and your talisman will disappear. But now you have an air Tiara.
Go into the altar with a full inventory of Rune essence. Make airs. Depending on your runecrafting level, you could make multiple runes every trip. Keep doing this until you use up all your ess. If you have 1k ess, then you will make 3k airs, and you can sell them all 45k which is a 15k profit from which you bought the ess.
Keep making profit and going up your runecraft level (Often called "rc lvl") or just make runescape gold. Soon enough you will be rich. And, sooner you will be able to make chaos runes, nature runes, and even laws and up!