This is my guide for you about easy money making in Runescape. Many people think the only way to make money is working, that wrong. If you want to make big money you have to merchant. Merchanting is buying something for a price, and later on selling it for a higher price.
There is one thing you need to know: It is almost impossible to become a rich Runescape player when you are not a member, because when you aren't a member you can't use the forums and there are many items you can't use. Conclusion: Non Members should become Member first (only 5$ a month).
Ok, to start of you need some money, otherwise you can't buy items. So I suggest you go and do something useful to earn money quickly (1 mill. is recommend). A good way to earn that million(if you are member) is to buy steel bars and make cannonballs out of then. You can buy steel bars for 650 each. And out of one steel bar you can make 4 cannonballs. And those cannonballs you can sell for 200 each. That means a profit of 150 GP on every steel bar you turn into cannonballs.
So now you finally have enough money to start your career as a professional merchanter. When you are playing Runescape there should be 2 windows active: Runescape - The Game, Runescape - The Forum. A Runescape Helpsite is optional. That way you can easily hop between the forum and the game.
Notes: While merchanting you are able to train your skill. You train one of your skill somewhere and post on the forums they have to come to you, that way they don't interrupt your training session.
Wear nice armor that way you can sort of intimidate the person you are selling of buying items of.
Let's start with something you can easily merchant: Treasure Trial Items. Most of my time I spend on merchanting hats (cavaliers, boaters...), they are easy to find and easy to sell(for a higher price). It's important you always put "Auction" in front of your Forum Topic. That way everyone will give a higher price then the person posted before(for your profit-optimization). You should continue to merchant with Treasure Trial Items so you can save up some money for the bigger work!
With the bigger work I mean Dragon Items like helmets, axes, legs... It's just the same as with merchanting Treasure Trial Items. Only here you have to be a little bit faster because there are many people that are willing to buy Dragon Items.