You need to be able to prove income and show tax returns, I've just done it. Your basically showing your concept works and you can sustain yourself, at this time you have no proof.
I've tried to open an account on a tourist visa and was given a form to get signed by immigration. I now have a DTV and so I'm going to try again. From reading various posts a residency certificate is the solution, I believe 200tb
That's my approach, but others have reported getting a bank account opened without issue even on a tourist exemption, I guess it comes down to the bank and the manager. Yes agents can do it, but if its doable and only a bank account then it should be easy enough yourself, unless there are other reasons an agent can resolve for you.