I always tell them no. My parents and grandparents drilled that into us as soon as we were old enough to say no. We were told the only people that had the right to come onto our property without warrants were game wardens and we couldn't stop them.
Hate cops who think the uniform should grant them automatic access to anything they want; free soda, free coffee, free meals, whatever. Working the farmer's market, I've seen the cops stop and pick things out only to make a token gesture of payment. At my stall that doesn't fly, when he made the motion to go for his wallet and then stopped like he did with the others I just looked at him and told him the price. There are no free rides for the po po. He got pissy and I got an ass chewing by the farmer's market people. Apparently they 'always' let the cops have freebies. Don't fly at my stall.
Nope, if they don't show a warrant, they aren't coming in. I can wait. If they destroy something, they can pay to replace it too I'll video them destroying it.