An easy money making way can be leveling RuneCrafting. You just need to collect and sell bones, runes, arrows or some other items which need high Runecrafting. Or you can level Combat to make serious cash, however it needs much time on leveling.
Many players considered mining as the easy way to make money, as what you need to do is spending hours leveling mining till you can get some rare ores which can sold for good prices. To some veteran players, they know how to use ores to make bars which can be sold at higher price than ores. At Mining level 15-30, mining iron ores can be good choice and at level 30-60 mining coals can be more profit. Besides, when you reach the requirements to hits, you can change your pickaxe which can be used for getting ores faster.
If you have some rs gold to start off, below methods can be good alternatives for you. Of if you have bought runescape accounts for sale with several millions of rs money.
Magic can be a good way for money making. If you have high Runecrafting, you can earn a lot. If you are starters, Runecraftinng air rune is nice for you. Just go to south of the entrance to Falador, there is Air altar outside there and a bank near there for you to sell air runes. Air runes can be sold 15-20gp each.
When you have some starting money, you can earn from getting a capital sold at least 220kgp. And you just need stay in the runes shop and buy runes. Buy death runes and chaos and go where there are crowded players to sell runes. Chaos can be sold 140gp or so and death runes for 280gp each.
If you have leveled Magic up to 55+, you can buy rune med for high alchemy. Rune med costs 10K each and nature rune costs about 250gp. After high level alchemy, you can sell them for 1200-1300gp each, which is quite profitable.
Hope this guide can be useful for you making fast millions of rs gold.