In order to search your house, the police need to have a warrant signed by a judge. In order to get the warrant, the police have to show that they are likely to find evidence of illegal activity at your house or other property controlled by you that they wish to search. A search warrant can be issued before or after formal criminal charges are filed. If your house is searched, the police must leave a list with you of what was taken.
What should you do if you are subject to a search warrant? Request a copy of the search warrant and cooperate with the police, because fighting with them will achieve nothing except you being arrested and moved to the back of a police car. Even if you have not been formally charged, you should plan on charges coming and obtain legal representation. When they search your house or office you could be in legal trouble, so take it seriously.