The problem with letting people stay past closing is that if they don’t leave voluntarily the only option you have is to evict them, which is a long process in California. We recently sold our home in NJ and stayed in the house 5 months after the closing under a “Use and Occupancy” agreement, which apparently gave us fewer rights (and protected the new owner more) than a standard lease back would. The purchasers knew that we wanted to be out of NJ after our kids finished school for the year, so they didn’t have much of a problem with the arrangement, but it could have been a problem for them if we were uncooperative. I don’t think I’d ever close without taking possession immediately upon closing.