I live in California where the Democrat policies have been in full force for 60 years, with massive government funded programs that give our tax dollars to pedophiles, ex cons, drug addicts and alocoholics under the guise of disability, free educations and priority to illegal immigrants, government unions demanding unsustainable benefits and wages, higher taxes a constant theme on our ballots, environmental regulations that require 8 different grades of gasoline throughout the state (which raises prices), hundreds of thousands of acres of farmland that cannot be farmed due to the Dems putting water for smelt over farmers, car registration fees so high that many lower and mid income people (especially the unemployed) are losing their vehicles, a community college system that is so top heavy it now takes 4 years for kids to finish a 2 year program for transfer to a university, and much much more.

I also found a drug pipe in their apartment, so I think they were often too stoned to care.

Not sure what kind of area you live in but sounds like he's renting to drug dealers or something.

Could we require our tenants to maintain and pay for this treatment in order to avoid any further pest infestations?

Generally, rental income has a pretty good tax treatment.

I basically posted a NO Trespass sign and also filled out the form and put a copy on the entry to the people that were issues.. they never came back Do A  Crime Free / Drug Free Addendum to your tenants..  

The only real issue is that you must satisfy the "Qualified Use" requirement in order to qualify for 1031 Exchange treatment. 

Assuming the surrounding parks offer the same amenities.Be very careful with septic systems/ lagoons/ treatment facilities.

I talked to him and he said he gets randomly drug tested for work and would not smoke marijuana because of that.

If you have a softener or filtration equipment like an iron filter, it'd likely be best for you to setup a quarterly PM from a local water treatment company to ensure your filters are changed out regularly and salt is added to the brine tank - especially if you have a boiler.PM me for a couple references of companies that work in the area...my family's business is in water treatment for commercial and industrial applications in the Midwest, but we have a couple companies we refer residential folks to.