Wow sounds miserable!

I would invest $50,000 in materials into it (and a lot of labor which is miserable hard difficult dirty work) and in return I would then start receiving $1,200 per month in rent income. 

Move on and why make them miserable they are already having issues.

You are miserable and clearly have don't real work to do.

There are many other ways a tenant can make your life miserable than simply not paying their rent (they may be a drug dealer for example). 

Against that, a small, fun thank you gift at Christmas is just part of that effort to make them not want to move and risk renting from a landlord that does nothing for them or worse, makes their life miserable.  

Most of Central CA is miserably hot in the summer and I would never consider living there (or investing there for that matter).

They could make your life miserable.

I personally would not want to waste potentially a year of life being miserable to make a few hundred dollars.

But I can guarantee you that if you are looking at this as a competition, you will be miserable.