As a male kitten matures, it becomes territorial. It may spray its living area with urine or seamen in order to "mark" its territory if it is not neutered.
If he's reached puberty, he may roam; also may spray your furniture and walls with urine to mark his territory. On the plus side, he'll be good company.
Fixed male cats are MUCH easier to deal with. The biggest concern usually is spraying, avoid having any other cats, especially males, around him. Strongly consider fixing him.
