I always offer something as I believe they are a guest in my home. After all, I invited them. Doesn't matter that they are getting paid, they are still there at my request.

I'm a military spouse and we move every couple of years. Every move we have done, I have bought lunch for the removalists, snacks and drinks. We are not paying for their time as Dpt of Defence pay them but they are doing a lot of hard work on our behalf. They are always very appreciative and a couple of times we have called the companies involved to compliment them on their workers and the receptionist always seems to know who we are.