Digtal B/W camera - obviously Leica M. You just have to own the bank, not to the bank.
For the rest of us
it is same as color pictures.
My Rebel makes good enough b/w candids. I put Zuiko 28 3.5 and it is OK for quick and dirty "street" with Rebel set to B/W.
Modern FujiFilm cameras seems to makes nice B/W.
If you want better B/W with DSLR, get FF and good prime like Zeiss.
I was looking for few days on Flickr group named something like: Street photography Monochrome. For me nothing beats 5D in digital B/W.
One thing which is huge in B/W PP compare to colors.
I'm not photoshop person, but in the Lightroom you have two bars to adjust colors.
Makes huge difference sometimes if you use them for B/W.