Hole saws are needed to cut holes in the walls and floor, mainly for the plumbing. They are sold individually as well as in kits. The kits can be very expensive and not many of them include the larger sizes that you will likely need. For this reason I recommend buying these bits individually (or buying a smaller starter set). The Milwaukee Hole Dozer Bi-Metal Hole Saw is a great option. It comes with the arbor already installed, and has a large slot on the side that makes it easy to remove the wood from the bit after your hole has been cut. You will likely need a 2-1/8 inch and 3-1/8 inch bit for the 2 inch and 3 inch drain pipes and the exhaust vents.