If possible, take photographs of each house: the outside, the major rooms, the yard, and extra features that you like or ones you see as potential problems. And don't hesitate to return for a second look.
Always buy “certified seed”. This is identified by a blue tag saying certified. By spending a few extra cents up front, you will save many hundreds of dollars along with the added aggravation of controlling unwanted weeds later. Choose the right grass seed, sod or sprigs for your situation.