It is also good practice to keep people with other chickens away from yours. It is too easy to spread disease if you let other chicken owners near your birds. It is tempting to show off but just think about having to cull your whole flock because of disease.
My sale chickens are in the shop on concrete so I just spray everything down with Oxine. I don't let anyone WALK in my pens EVER. That would be very bad indeed

When I have bought from NPIP people they will let me go up to the pens, but that is as far as I get to go. I also use Oxine on MY shoes BEFORE I get near their birds and when I leave.... that is just me.