Two years ago we moved in to our home, and the house next door was in some disrepair - siding missing, lawn unmowed, windows cracked. We were assured by the patriarch in residence that it was temporary, as the boys (his sons) were in the process of making repairs. Fast forward to the father in a home with the mother and the house rapidly deteriorating as the siding gets worse, junk piles up, shady characters come and go with alarming frequency. Now the fence between our properties has been broken by people climbing it and running thru our yard, leaving food wrappers and other debris, discouraged only by our large and vocal dog. Things are getting worse by the day. Who are the right people to complain to?
Your city building department could get involved if the home is no longer in repair enough to meet city building codes. I would start there. If people are trespassing on your property, call the police.
j/k.
I agree this is likely your easiest and possibly most effective option. In the alternative, you may wish to consider a filing nuisance action against the property owner, but you’d need a lawyer–and might learn that the owner simply doesn’t have any assets available to fix the property or satisfy a judgment.