@angel*jen wrote:Thanks everyone for all your suggestions and advice! I wasn't sure if I was just being silly but I am unhappy with him coming onto my property. I will call the real estate tomorrow. Thanks again!!
Could you come back and let us know what happens?
I'm a little more direct and would confront the guy, but can see why you might not want to. Plus you get it on record in case you have future problems with him.
Maybe get it on video in case he denies it.
Hi angel*jen,
Sorry to read you're having the landlords son take too much for granted. What a tosser!
You've been given really good advise already.
I'd just like to step it up one bit further and suggest you email your property manager rather than just telephone them.
That way there's a record of your concern over this tosser's actions from the begining.
Also ask your property manager to understand how anxious he makes you feel and for your concerns to be dealt with bearing this in mind please.
I know this sort of thing can be awful to do and make you feel very uncomfortable but it's obviously not a good thing to have this bloke just walking in to your own yard - univited... no matter who his darn parents are!!
You go girl and get this guy sorted out. Personally, I'd be calling in Jimmy! 
