If your business is portraits, you'll want to invest more in lighting before lenses and finally bodies.
Or the other way around.
Back when I started, a portraitist could go a long, long way with a single lens on a medium format camera and window light. Penn, Karsh, Avedon, all of them did some of their best work with no more than that.
The camera is important because portrait work at its best and most lucrative involves the ability to print large and with good detail, not to the same extent as art landscape, but more than most. That's why portrait artists used medium format and larger as did landscape artists. I did more profitable portrait work with a Yashica medium format TLR than I could have with a Nikon F.
So the camera does have importance for portrait work.