The Runescape economy is built on work that takes time. While you’re building up your skills, you also have the chance to make money. Making armor and weapons and then selling them for a profit is the classic method. Of course, there is money to be made my doing quests. People with free accounts have a harder time making money due to the limitations of what they can do in the game without purchasing a subscription. So if you want to make more money making things, spend some real money and get the full version of the game.