Usually probation requires that you submit to searches of your home and person by your probation officer without a warrant. They can show up and do random searches just as they can require you to do random drug and alcohol testing. The frequency of this will depend on your probation officer and the norm for that particular probation department. Consult with an experienced criminal attorney in your area for a more in-depth answer.
Mr. Austin is correct. I have heard of them doing the searches in Ottawa County. I would say it is rarely done. However, if the probation officer gets a tip or you test positive for drugs, then I would expect some action. So, just keep you nose clean. Good Luck!