Well first of all if the property is purchased at foreclosure and the proper steps taken to transfer the deed and to evict those remaining, you do not need permission to enter the homes.  And you should not enter a home that has not been legally vacated through eviction or what ever because it could put you in physical danger at the very least or subject you to various criminal claims such as harassment or stealing should you enter and they claim something of value was missing after you left.  No employer should put you in that position.  Good luck.