Ghosts are life after life entities who survive the process we call death. I believe that ghosts are proof that we live again after death. I personally know of none. I have heard about serial killers, but I don't know them personally. This same logic applies to ghosts.
Ghosts are for the most part good spirits, just as people are for the most part good.
Yes, there are evil men and there are evil spirits, but the odds of having them in your home are the same as having a serial killer come to your home. Fear is based on not knowing. In most cases, blessing a home has no effect on the spirits that dwell therein. They are not bound by the same belief systems that you operate under. Perhaps instead of trying to rid your home of ghosts, you should try to understand them and see if you could help them resolve their problems.