What is a good body fat percentage for being at? When I was in college had a natural sub-10% with ripped stomach. Kinda intrigued to get back there. But then my Y instructor worries that I should stop at 13% or so and spend about a year trying to build muscle (staying at same weight, gradually changning the balance.) He thinks below 10%, I will have a hard time producing test, especially as I am older now.
I think the guy at the Y, while having good intentions, is going to hurt your progress.
Most methods of measuring BF are inaccurate, so the difference between 10% and 13%, outside of to a competitive bodybuilder, is negligible and pointless to worry about. You will look great at both assuming you have some muscle mass.
You should get to a level of BF you are comfortable with. Don't bother getting the number tested, who cares what it is. Don't shoot for a specific number, shoot for a look in the mirror that you are comfortable with and then maintain that weight. The most important part is your self image at this point.