Runecrafting: You are encouraged to mine rune essence, it is a fast and still used way to help people level up runecrafting.Now runecrafting is boring but, if you think about it as an achievement, You could mine up to 1k rune essence per day, now if you turn 1k rune essence to law runes. HOLY SHE SHIVERS thats about 500k
Wood cutting: The best places for woodcutting are
Normal: Outside Lumbridge castle
Oak: outside Varrock castle
Willow: Draynor/ Outside lumbridge castle
Yew: Outside Cabbage patch farm
Magic: gnome village
Mining: Mining is a very hard skill to level up but gives the most amount of cash through out all stats used. Lets just say u mine 1k iron ore. thats 100k with 25k mining exp, That is a great amount of money for a money maker
Melee:Melee, you can either kill monsters for money or drops. Rare drops dont often come up. so the monsters i think are the best for you guys is: Lesser Demons = Rune Med, Runes, Coins, Large amounts of fire runes
If you cant kill lesser demons, kill hill giants they give money drops and big bones which are 100-200gp ea
MONEY MADNESS
This is one of the best tricks in the book, PVP its a 50/50 chance of losing and gaining money, if you had looked at my pvp guide you could take someone out easily. Try to build ur Character as as pure, which is a fastest way of killing someone.
When u get a wierd drop like, lets say 3rd age carafe, You might think that is a members item. NO exchange it to mandrith(only appears in pvp worlds) and u can get a large amount of cash.