It went fine for the first year until we found out her boyfriend was growing a pot garden on the property.

I think for them they like the larger units and many have planted gardens in the back yards.

One roof, one pest control contract, one parking lot to maintain, one gardener, etc.And I personally really dislike duplexes as a renter.  

Secret pot garden in the closet maybe?  

In my experience, it's best to pay for a gardener.  

I have allowed some requests like I want to plant a garden or I need storage shelves but the sooner they start asking for changes to the structure the more likely they are high maintenence.You could also opt for a pm.

I am thinking about doing a rock garden, super low maintenance plants or mulch.  

Last week I got a call from my gardener that my tenant turned off the irrigation 2 weeks ago, because she did not want to pay her water bill!  

I think this could be a definite golfball in the garden hose. 

Soon, you will be limited to indoor water use of 55 gallons per day, but there are exceptions for your swimming pool and outdoor gardens.