Most likely they will have a conditional search warrant ready to go for when you're in hand cuffs, once you accepted possession they are now able to search your vehicle and house
I am not sure how that works with storage units, but i can only assume the same.
I don't even know how it would work with roommates, say the package is in my name, do they get to search my roommates room and car etc? Interesting questions that I'm not sure i want the answer to , cuz that would mean I'm likely in cuffs lol
I wonder what the least evidence needed for a conviction would be. Say you just have syringes at your house, is that all the proof they would need? I would think it would be possible off that