As you reach your twenties, does your arm hair, mustache, beard, leg hair, and belly hair condense or is it usually already all there by the time your 19 or 20 years old?

For most, that is set about the time you turn 20, or before. You may start growing hair in other places like your back or butt cheeks as you age. Women may begin growing chin, nipple hairs and belly hair when estrogen levels begin to fall.