Build a rep or yourself first off, you won't profit much doing anything (GP Flipping, or selling accounts) until you've acquired a somewhat decent rep.
One thing I'd suggest is paying people to create NMZ ready accounts for you. These are fully quested NMZ accounts with 70attack, 70strength, and 70defence. You can then either afk NMZ yourself whilst studying or in your free time, and sell the accounts off at max melee stats or rent them off as stakers. Or you could pay somebody to max them out, and then do the above suggestion.
You could always pay new-ish trainers to train up some pures and sell them off for a profit. You won't profit much at the start considering you've not really got any rep, but overtime it'll become more and more profitable.
If the above options aren't appealing to you, your only other real option is flipping GP.
Again, you'll have to somewhat build a rep for yourself before it becomes profitable, but over time it could definetely becomes a small source of income. Simply buying GP for $0.85 and selling it for $0.90 is a quick 5.25% profit on your investments.
Once you build a rep for yourself, the options become sort of endless. You could start up your own skilling or questing services, and then hire workers to complete the jobs under your supervision. You'll pay your workers a commission of the price that you charge, and keep the rest for yourself. You just have to make sure to hire the right workers.
@Karter99
