Hand truck http://en.wikipedia.org/wiki/Hand_truck is a very simple machine and is part of any movers toolkit.

You really want one of these for the heavy stuff though:

http://en.wikipedia.org/wiki/Stairclimber

It makes a world of difference.

I have a really solid aluminum hand truck with stair skids on it. Most appliances weigh less than 250 lbs (I would guess average would be 175-200 lbs) and I'm able to move even the heavier ones up and down stairs by myself (not always easy!) It can be pretty physically demanding work sometimes, and I will ask questions to find out how difficult it might be to remove/deliver an appliance and bring help if I need it.

I'm thinking he gets a little bit of free labor out of his kids :)

Not yet :) They are all years old and younger. When they are teenagers though...