He then just had to run a roller half way up the walls to freshen up a unit, normally (unless they were smoking in there against rules). 

I thought about getting headphones but if they cancel out sound, they may prevent me from hearing a sound that I need to hear in the middle of the night or in an emergency like my bell, a smoke alarm or my cell phone etc.

Do inspections every 6 months, but just put on the notice of entry that you will be entering to check smoke detector batteries and check for any plumbing leaks, and to please let you know ahead of time if there are any other maintenance issues you should look at while you're there. 

If he got busted smoking a joint in the park  or with a small amount of marijuana I'd have no problem.

(Tenants would probably freak if the PM started taking photos inside the home.)It's normal to do an inspection twice a year, where the tenant is informed they will be checking smoke detector batteries and for plumbing leaks and to inquire of any other maintenance issues the tenant has. 

This includes criteria such as no smoking, no pets, 3x income preferred but 2.5x acceptable with additional security deposits. etc.  

We did inspections every 6 months (26 unit building), and would check smoke detector batteries as well as look for leaks or running toilets.And if the water bill went up significantly, we'd do additional inspections, looking for the inevitable running toilet.Next best option is to use month to month agreements, so if you suspect a unit is going crazy with the utilities, you can get rid of that tenant.  

My darn spell check makes it look like I often drink and post, fact is I don't drink or smoke.

Landlords really need to completely understand their right to say no to "reasonable accommodations," and any applicant who happens to belong to a protected class - just because someone's in a protected class doesn't mean I have to allow them if they also smoke and I don't allow smoking, or because they have an emotional support dog that's a pit bull, etc. 

Whenever an applicant started out with requesting a discount, or complaining about this or that, or asking or demanding that we provide this or that (from blackout curtains to guarantees of never smelling cigarette smoke...), I learned over many years and many tenants that this is a tenant I will have wished I'd never rented to.So, take it from me, if there is any way you can deny this applicant, do it.