A healthy level for the average male is roughly 10-20%. However to get your abs to show you need to go beyond average. So if you can build up your muscle mass your body fat weight could remain the same but as a percentage it will drop. The double whammy of greater muscle mass (%) and falling body fat % (only) may make your abs more visible.
So if you want to say hello to your abs, you'd better start taking your workouts to the next level!