There are many ways to make money on Runescape
Personally i'd say flipping is the safest way of merching on Runescape, and it's fun!Flipping has a very wide spectra, and the more experience you gain - the better you get! Don't give up if you fail, because you gotta fail to learn sometimes - and it gets easier.
To start flipping I recommend at least 10M cashpile to really take the fully advantage of flipping. Lower cashpile than that and other ways of making money is faster.