You, should never encourage the wild animals to nest or feed in the surrounding as they would expect a safe dwelling place in your property., Look around for the common symptoms of Possum infestation.

Possums are nocturnal and remain active at the nights. Your nights would become restless for their activities at the night.
If you find droppings in veranda railings or at any other locations, possums are either dwelling in your property or are paying regular visits.
If the surrounding smells like rotting fruits, the possums already are dwelling in your property and the smell is from the stored foods in their dwelling.
If a possum dwells in your property without your knowledge, your pets, i.e. cats and dogs, would become restless and keep on howling.
If you find the garbage loitering every morning, it is time to take actions to prevent the possums from accessing your property.