Do just a little bit of farming runs. Even if you just do one a day and only 1 place, you are going to earn money steadily (that is what I do, and
OSRS gold also I have an 8mil bank). You probably could train power on lower demons, they drop ashes that are worth ~600 gp each, along with some elchable items. Guthan's might help considerably, but you couldn't afford it for a while. Kill them at the Karamja place beside your lave thingies.
They've a nice reward worth a bit, then find a yew tree to cut down as you have the auto-banking effect still on. You receive the auto-banking for some number of minutes based on how much you helped kill tree.
It's undoubtedly the fastest route to 10M but it's stable and will get you there eventually. A goal like this is not easy because the temptation will always be there to spend it on crap but to do it using one of my methods: Require 10k and purchase oak planks for -5% and see if you get some. The 10k is just a tester to find out whether they purchase and you should wait 5-10 minutes.
When they don't purchase then increase your bid 1-2gp till they do buy. Sell 1-2gp under middle price. Generally you will get 10-12gp for every oak plank (which usually means you ought to set your purchase price at 13-17 under mid) you do that may not seem like much but the next time you will get longer, and more and more. . .before
buy RuneScape gold you know it you will be trading 25,000 frequently and bringing in 300k per trade.
The Wall