Now, do you know what caused that spike?

After I found this out, I checked the water history and found payment spikes throughout it likely caused by leaks.

Electric can also spike in the summer with A/C.

That has helped me avoid missing the local timing spikes from various events in the area from a pricing standpoint.

I know there will still be unknowns that cause fluctuations in income, but taking out the largest spikes seems to me a really appealing idea. 

However, you assume the risk of a spike in the oil prices.

I know it seems like a lot now, but the way rents are spiking, these will be way under market 2 years from now.

I would tell them there are cameras and if I catch them again they will be reported for trespassing and charged for damage to my lawn.Then I would either install a camera or I would install some very long, sharp spikes in the dirt to guarantee at least one flat tire if they did it again.Then, and only then, would I consider the additional expense of a fence, boulders, or whatever.

So if you pm and do your own maintenance Id say 400 a month average if you dont spike the expenses upto 600 to 700.  

Based on your clientele I was hoping for something with spikes and chains on it - so I give you a 6 :D