Why does he want to be seen as JEWISH by other Jews? For acceptance? Acceptance might not follow conversion, especially by people he knew before and after...and then what? If it is for some reason other than wanting it for its own sake, then I would advise: in my experience, there is very little that a person cannot do while living a Jewish lifestyle but not formally converting. If the young person is deeply wanting to read from the Torah during a formal service, or perform preparation-for-burial rituals, then I guess conversion is necessary. If the young person wants to celebrate Jewish holidays, welcome Shabbat, keep kosher, pray, study Torah, join a shul, praise G-d, get circumcised, support Israel, etc., there is no need to convert. If the young person wants to make a formal rejection of Christianity, there is no need to convert. If it is to match family members' Jewish status or something like that...I guess conversion is necessary.
I have observed that many young people today seem to me to be suffering from too many choices in life, and they go about cutting themselves off from various possibilities, lest they fail at them. So I am wondering whether this person is wanting to cut himself off from something by converting, and I wonder whether being Jewish from now on is really what he wants. I would want to know more about what the motivation is. I would not want him to convert to Judaism, and then renounce the conversion.