There is sort of a East side/West side thing when it comes to investors that almost sounds like the rap battles of the 80's. 

If you do go with a non-connected lock please change the codes often, I often compare it to a hotel in that if the front desk told me the previous occupant's keys still worked during my stay I'd be sort of annoyed.FWIW, we use ResortLock from Lockstate (no affiliation, just what we use) on all our properties. 

You could always use those to prove they were smoking up; with that proof you can either move to evict or simply hold security and at least have some sort of proof.If you install a marijuana smoke detector I wouldn't even tell them what it is (aside from a smoke detector) as they might try and disable it.

Thankfully I think that "click bait" of sorts is quieting down a bit. 

But you might be able to work out some sort of agreement with a tenant to fill that role for a slight rent reduction.

I want to ensure that I follow any sort of regulations and safety standards but I don't know where to even start or know how to estimate rough costs.

The walls on the second floor show white chalking and also some sort of drip marks.

Both on the purchase end and in the execution of who is going to handle your properties.There are a lot of PMs that take on hard to manage C and D and do well with it because they know they are going to be able to charge all sorts of fees to corral these types of tenants. 

What sort of terms would the USDA contract contain? 

Unfortunely, it seems you cannot be any sort of deterrent from others investing into the program, even if means losses to accommate unlicensed jobs.