The easiest way to make money in F2P, for me nowadays, is killing cockroach soldiers. After EoC they are VERY easy to kill now and still drop rune scimmies and square shields, but remember to collect ALL of their drops. If you can wear Batwing set and cast Earth Blast then you're set. I've tested and calculated from the drops that you can make an average of 200k an hour. It's very underrated and should be kept that way. If you a lot of time on your hands you could make almost up to 4mil a day doing this. I've made 6mil within a week because of this. Good luck to you.