I did not need to do that. I applied in Denmark, and I gave them a screenshot and a link to the website you will find a link to in my profile. I was not asked to prove an income from the website - which was good as I don't really have an income from that.
I was asked for proof of my company's existence, I send them a copy of my VAT registration.
No proof was needed for an income. I am retired, and have earlier had NON O multi entry visas, and I was a bit nervous that they would know that I am retired and thus refuse to give me the DTV. However, I got the DTV.