Opossums are an invaluable asset to our city and help us to keep an important balance. They are extremely low risk for rabies, want nothing to do with people, and will, when they feel threatened, open their mouth and hiss to scare you, and then play dead if it doesn't. Domestic dogs and cats, if vaccinated yearly, have nothing to fear from opossums. In fact, the only real threat is that your dog is going to severely injure or kill the opossum. Opossums eat rats, snakes, bugs, vegetation, and just about everything else. It's not uncommon to get an opossum under your house if it is of pier and beam construction. Opossums do not, as a rule, become destructive or intentionally cause damage to property. From time to time they will grub in gardens, get into unsecured garbage cans, and go fishing in resident's koi ponds.
To discourage opossums from coming into your area, feed dogs and cats indoors, secure garbage can lids, and secure the perimeter around your house (if it is of pier and beam construction) after making sure that there isn't anything actually under there at the time. Remember, opossums are extremely beneficial to you, and trapping them is discouraged as it depletes our city of an important (and free) resource.