Typically they tear your shit up unless it is obvious what is going on and they find what they are looking for easily enough. Everything depends on location and specific circumstances, of course, but especially when a raid involves suspicion of things like distribution of higher scheduled substances and you can bet any kind of cultivation.
At one point in my life I was the friendly young junkie who lent a hand helping cleaning up after they hit one of the houses my 'favorite' dope dealer did business out of. Essentially these people or persons, whomever has direct control over the product, will make arrangements with individuals or families who are tenants. The associated tenants are often distantly related to the dealer, or otherwise share some perceived familial connection. Location is key, so the dealers will usually make arrangements primarily with individuals and families living in government subsidized housing in the 'projects'. Sometimes the associated tenants have a habit they need help with, and so receive drugs in exchange for allowing the drug dealer and his associates to conduct their business there. Other times the arrangement is different, such that a dealer may be paying any additional living expenses accrued by the associated tenant.
These houses in the projects get raided all of the time, probably in part because the transactions taking place are frequent and quite obvious. So, when the cops bust in and they seem to be having difficulty finding any drugs it really pisses them off and they will go hay-wire trying to find them.