Better start concentrating on the way to 99, not what you should do once you've got the chance... And if you would take the old fashion approach to thieving: crack the wall safes 270 times RS Gold, then change to knights... You would need 152,643 knights to get to 99, netting around 7.5m gp. Trust me when I tell you that woodcutting is the best option.
It took me a day or so to get 1k magic logs,sold em in 5 minutes for a cool one million coins.Not only that,but you figure that woodcutting has more of a market than the other skills,seeing there are fletchers,alchers,construction workers,and of course,merchants who will buy from you,and sell to their friends for higher.
Profitable selling is easy because there are hundreds upon hundreds of people buying yews or mages from the forums, not to mention worlds 1-12 on the seers and Varrok. 99Woodcutting, a great cape, and an incredible emoticon is worth the effort.
Also,I have limewire,I suggest getting it for free, and then playing your favorite music while you cut wood, makes it much more easy to use, because you are so into listening to the music that you forget about time and it all zooms through Buy OSRS Accounts. The cape can be paired with range or pk armor, so you won't need to worry about getting it wrong. I hope that my suggestions can be useful in the future.