as per OP question , he wants to bang his boss not asking if it is ok to bang your boss
if we would think mainly about risks , no one would bang women . Risk of being arrested , risk of getting and STD , risk of an angry ex , risk of , risk of etc etc
if he will be fired because of banging his boss then it will be a lesson learned . He is young , most likely his job is not that serious to begin or well paid . He can easily find another job , maybe even better paid
if you want to help him out , then try to give him some advice on how to actually bang his boss . The lessons after is his to be learned . This is how you learn , by also doing dumb stuff from time to time