There is no minimum income requirement. Main financial is the 500K in a personal bank account. You do not need a website to gain the DTV. Several online teachers have posted their success on the main DTV FB group page. The DTV is a multi-entry visa you can come and go as you please with the 5 year term.
Ok, it can be confusing but the DTV is not one fit all embassies vary. I had 500k for 3 days when applying in Taipei. One friend had it for an hour before submitting in London, one had it for 4 months to apply in Laos.
The bank letter certifying the amount being approved is embassy specific. I submitted such a letter in Taipei and was told they would not accept it even though the website stated it was acceptable. Was told 'we want to see transactions for the 500K" Had to rush to get bank statements printed out.