I never expect any rapper/vocalist to bring a mic.
I do however often take the opportunity to tell them about some vocalists I know who bring their own mic rig just like guitarists bring their own guitars. I show them some examples who have 8-10 space racks with 1-2 wireless channels, IEM, drawer with wired mic (s), another drawer with towels and other stage accessories. Front or rear panel with XLR, power and a couple USB ports for phone charging. One or two even have their own money channel effect.
I have built a few of them for people over the years. I think its a huge differentiator for the vocalists who bring their own rig.