We want to keep him as a house cat. Thank you for your help. In addition, their urine seems to have a much more potent odor. I do not know the exact statistics on the percentage of male cats that spray if they aren't neutered, though. These are expensive habits if he gets bitten frequently and develops abscesses or if he gets hit by a car and survives during a trip to the girlfriend's house.
Neutering is by far the most effective method of preventing spraying behavior.
If you elect not to do that and he develops the behavior there are some medications that seem to help limit spraying, such as diazepam and buspirone. Keeping him on medication isn't always a great idea, either, though. If you plan to get him neutered it is best to do it before he starts spraying but it will probably work even if you wait until he shows signs of this behavior. You can always wait and see what happens and then decide. My male cat is 10 years old and has re-developed a spraying problem.