Not that the show isn't already unrealistic, but that would just be taking it to a new level. No way he would pass character & fitness.
It is a show, anything can happen, I'd imagine he would be a well paid PI, but it is possible he takes night law school in 2 years while in jail and then passes the BAR. He always did amazing work while a lawyer, parents died he wants to help people, I don't know I can see them making it work, however unlikely...
Or he can be the paralegal and rachel will be the lawyer