Treat the wet zone as a system.
Tile, grout, and a new vanity do not make a bathroom waterproof. Ask how the shower or tub surround, transitions, substrate, drains, penetrations, and any existing damage will be handled. The answer should describe a coherent system, not only the surface finish you can see.
Ventilation deserves the same early attention. A fan, duct route, exterior termination, and the way the room is actually used can affect moisture control. If a bathroom has recurring condensation, staining, or soft finishes, bring that history into the conversation rather than designing around it.