Anyone who has played Runescape for any length of time can tell you that it is much harder to make money as a non-member than it is as a member. Many non-members become frustrated due to this. From the moment they finish the tutorial, they see players with high priced items and wonder how they will ever be able to acquire such nice things for themselves. The good news is that there are ways to make money as a non-member, and some of them do not require that you have high level skills to do so.
The most important thing to keep in mind when determining the best way to make money is that it will take time. There are very few ways to make a lot of money quickly. For that, you have to rely on lucky drops. Lucky drops do happen, but they can't be counted on. What you need is a reliable way to make money. You cannot expect to get rich fast, but you can definitely expect to watch the pile of gold pieces in your bank steadily increase if you follow this guide.
The Grand Exchange is a very good outlet when making money. The Grand Exchange allows you to put your items up for sale without having to haggle with other players. Selling at the Grand Exchange also means that you can get the same price per item no matter whether you have ten or thousands of that item. Before the Grand Exchange, it was often difficult for players to sell a small amount of an item. If they were able to find someone to buy the small amount, it was usually a merchant who would buy for the lowest possible price from many players, then sell his collected goods at a much higher price, as he was offering them in large quantities.
If you've been playing for any length of time, you know that item prices fluctuate. On the Runescape website, you can find the Grand Exchange database by hovering your mouse over the link that says "Game Guide", then clicking on "Grand Exchange." This database will show you the current price of all items that can be sold via the Grand Exchange. This allows you to find out the prices of items without even having to travel to Varrock. The database also tells you whether the price has been rising or dropping. You can also find information as to what items are traded most and what the most valuable items being traded are. This is important. Finding that an item has a good selling price doesn't make a bit of difference if no one is buying it.
As a non-member, you will find that the only way to really make money is to provide things that members want, but don't want to collect themselves. The things that sell in quantity and are used frequently are the best items to sell. Many of these items are things that don't provide much if any experience for the person collecting them. That is why many players are willing to pay well for them. It is often tedious work to gather the supplies, with little experience compensation.
There are many guides out there, and most of them contain the same items to gather and sell. The only problem with these items is that they're popular money making items, which means the areas will be crowded. Keep in mind that there are sometimes multiple places in which to gather certain items. Some of those areas will be better known, therefore more crowded than others.
Cowhides and leather are a popular money making item. There is a cow field in Lumbridge and a couple more south of Falador. The ones south of Falador may be further from a bank, but they're also less likely to be as crowded. The one next to the crafting guild also has the advantage of being close to a tanner if you have the 40 crafting it requires to enter the guild. Keep in mind that people pay for convenience with a lot of things, so you will make more selling leather than the untanned cowhides.
Yew logs require 60 woodcutting, but are a very good source of money. There are yew trees between Lumbridge and Draynor, north of Varrock palace, south of Edgeville bank, and south of the Falador city walls. There is always a market for yew logs, as members use them in vast quantities for fletching.
Fish are a pretty good bet if you know which fish to obtain for selling. If you have the level to catch them, lobster and swordfish are great money. Unfortunately, the only place to catch them in non-member worlds is on the island of Karamja. This is a pretty far distance from a bank. For lobster and swordfish, you'll want to sell the fish raw, as it's more profitable to sell to people who are looking for cooking experience. Another idea for lower level fishers is anchovies. Anchovies which are caught with a small net are bought by people wanting to raise cooking by making anchovy pizzas. You'll make a bigger profit with these by cooking them before selling them. You can fish for these in Draynor, so you're very close to a bank.
Clay is an item used by members for construction and for making teleportation tabs. Clay can be mined with level 1 mining. The best place to mine clay is south of the west Varrock bank. You'll make more money with clay if you first make it into soft clay. You do this by filling a bucket with water and using the clay with the bucket of water.
Ores and bars are always in demand by people trying to raise their smithing levels. It's generally more profitable to make the bars and sell them. That saves smiths a step in the chain to making smithable items. This means you can also gain a bit of smithing experience yourself.
Always keep an eye on new skills and things that are popular at the moment, and try to profit off of them if you can. Make good use of the Grand Exchange database to do this. There are always items in demand, and the fewer of them being gathered, the more people are normally willing to pay for them. Try to find those items on the database, and make a profit while filling that need. So get out there and earn some money.