After the "Trustee's Sale" which concludes the foreclosure, the new owner [which is sometimes the foreclosing bank] cannot legally take possession without then going through the eviction process. As with the other kinds of evictions, the process does take time, during which you can sort out your options. The former owner is entitled to a 3-day notice, and any tenant of the former owner is entitled to 30 days' notice, before the eviction lawsuit can be filed. If you are such a tenant, but get only a 3-day notice, you have a tactical advantage when you start fighting the eviction. Your lawyer can explain the details of these approaches and help you decide how best to handle the problem. Good luck.