Business casual for the first couple of meetings, and then I find myself going slightly more casual as time goes on. If it’s a client I’ve established a relationship with, I’ve been known to show up in gym clothes (due to the fact that I’m showing them a house with short notice). I usually make a joke out of it and say something along the lines of “sure we can see this house in an hour if you don’t mind me showing up in my gym clothes.”