Would it be permitted to set up an online sports betting website for oneself? If the answer is no, would it be permitted to assist another Jew in setting up the same website as a professional service.

It is not advisable to participate in anything to do with gambling as it damages ones soul, Neshama. There is a disagreement amongst the Poskim with regard to gambling whether it is allowed or not. You should consult you Rabbi on this matter. Rabbi Yosef Weitzen