One of the best ways to make money in Runescape at this current time for pures or people who do not have high stats is by burning willow logs and then collecting the ashes. Below i will explain the simple 5 step process in making money from collecting ashes.
Step 1) Purchase some willow logs and a tinderbox from the Grand exchange.
Step 2) Begin to burn the willow logs at the grand exchange or anywhere else that is good for burning logs such as Edgeville bank or Falador bank etc but i recommend just staying at the Grand Exchange as it will make it easier when you have to buy more logs and sell your ashes.
Step 3) After you have burned the Logs wait for the fires to die out and then pick the ashes up off the ground.
Step 4) Bank the Ashes and then restock your inventory with willow logs and begin repeat what you have just done.
Step 5) Once you have burned all your logs go to the Grand exchange and sell all of your ashes for a nice health profit of around 300gp per log that you burned.
Willow logs - 11gp
Ashes - 343gp
343 - 11 = 332gp per log that is burned
332gp x 27 (invent spaces) = 8694
In one hour you can make roughly 17 trips which equates to about 152k. That is today's rate obviously prices can rise and fall all the time this therefore means that you may make more money than this or less depending at the price you bought your logs for and the price that you sold your ashes for. You can also expect to make 40k firemaking Xp per hour!