Their are actually quite a few ways you can make money as a free person and still get decent experience at the same time, that doesn't include Merching or Flipping items
The Best way to Make money is too mine. simply mining iron ore once you are capable of mining it is the smartest way to level up and still make good money at the same time. I highly suggest you do this method of mining until you are at least lvl 60 mining. Once you are lvl 60 mining or higher, you can then buy some nature runes and superheat steel bars as you mine it. If you are a skiller, I highly recommend you mine iron ore until you are around lvl 75 or higher mining before you mine full loads of coal. Once you are around lvl 80 mining, You get experience at about the same rate as iron ore, but with a little more money. If you happen to be one of those people with 70 smithing, it would be smart to get a coal bag from the dungeoneering rewards and mine adamantite ore in the wild where the hobgoblins are. If you superheat adamantite ore, you can raise mining and smithing and still make around 200k per hour. Once you reach level 84 mining or higher (with dwarven stout), you have the capability of mining the 2 runite ores in lvl 46 wild. Their are revs that attack you at will and many people mine runite ore too. Normally, half the worlds I hop too when mining are already taken by other miners. I usually make from 400-600k per hour mining runite ore which makes mining the best way to make money for free players.
The 2nd best way of making money is runecrafting. Right now earth tiaras profit the most money when runecrafting them so I suggest you runecraft these when working on your levels. A fast way to get from 1 to 50 runecrafting is to buy around 4200 air talismans and 4200 tiaras. if you make air tiaras at the air alter, it is possible to reach 50 runecrafting in half a day's time. Not very long compared to making runes. The problem with this is you lose around 2 million worth of gold taking the fast route. Once you have 50 runecrafting, you have the option of going to the runecrafting guild and doing a mini game called the Great Orb Project where 2 opposing teams compete to get tokens. These tokens can be spent on runecrafting clothes, runecrafting staffs and talismans. Water talismans currently cost the most money right now and if you spend 7 hours of doing 50/50 games, where 1 team wins half on purpose and the other team wins the other half on purpose to get even coins every game, you can get up to 1.2mil gold worth of water talismans and sell them in the grand exchange for that much. However, doing the Great Orb Project is slow on Runecrafting experience.
The third best ways of making money is by simply wc'ing yews, mining iron ore or superheating steel bars while you are mining. These all make around 100-120k per hour and raise your experience at a pretty fast pace.
