In talking with attorneys who represent alleged pot growers and drug producers of various types I have heard how landlords specialize in in renting to folks engaged in this line of work. Often times landlords can charge exorbitant rates for turning a blind eye. However, those same landlords are subject to property forfeiture laws if the arresting agency can show knowledge on the part of the landlord. I would think that above market rental rates would be one such indicator of knowledge as well as complaints from nieghbors.
For those readers who might be thinking that they can benefit from drug trade without actually dealing in drugs, you may want to think again.