If one is paying the rent, no harm, no foul.

We are remodeling another duplex where each side had dogs and the smell in there from dog urine is horrific, plus all of the subfloors under the carpets need to be sealed now with Kilz to block the odor.

. :-)You can fight odors if there are any (though I don’t think you mentioned it.) with an ozone generator while the property is empty.

If he doesn't, then you can try a couple of different things that have worked for me:1) Offer him an easy, no fuss, no foul early out with an Early Lease Termination (ELT) fee.  

It's honestly a very strange odor.

Medical marijuana, recreational marijuana and street marijuana all leave behind a nasty odor when burned that gets into carpets and drapes and smoking can leave a film behind on walls and other hard surfaces.it doesn't matter what the source is.  

Then you have your complete criteria written up and you can email it to yourself, so if anyone cries foul regarding fair housing, you're covered. 

You can also insist on renter's insurance and have your LLC or yourself listed as the additional insures.I do not allow smoking in my units all, it greatly increases the cost to turn them and remove the foul odors and yellowed walls.Do beware of any discounts as an employment discount is definitely discriminatory.

Do they smell of cigarettes/weed, diesel fuel, body odor?

If a tenant just goes "no harm, no foul" and doesn't earmark the rent money in a bank account to show they were paying then in court it is likely the tenants lease will not stand up.