Paint walls from the top down. If you are using a roller, start by making a large "V" or "W" (3'x3'). Then fill in between the gaps, blending into your initial stokes. Always work from the unpainted into the painted area.
Sellers will sometimes opt to remain in the house after closing via a short-term rental agreement. As the new owner, be sure the purchase contract and rental agreement stipulates that the sellers repair any damage they cause after the closing date.