Not many people want their weddings shot in B&W, so that limits you unless you also print colour.

There is a niche market for B&W weddings but it'll always be small, the reality is that you can custom print as a sideline for extra income but unless well established in a major city you'd never make a living from it.

That's talking from experience, I used to shoot occasional B&W weddings and at one point at we did all the B&W printing for a commercial lab, they specialised in processing for wedding/portrait photographers and amateurs & even early 80's there was little demand for B&W. My suggestion is get two or 3 regular clients the income will fund your own photography without taking up too much of your time. Then see what happens. I had some regular clients and I did all their B&W printing for about 30 years.

Ian