When two individuals know nothing about each other, there is no way they can have a relationship, unless at least one of them knows the other sparking a two way knowledge and awareness that will finally end in a relationship.

As for having a relationship with Imam Mahdi (as), he is one end of the relationship that knows us very well and has affection for us.  What is left for us, the other end, is to know our imam well and become worthy enough to see him, as has been the case with many righteous and pious individuals.

A relationship with Imam Mahdi (aj) can be in one of two ways; an inner relationship or an in-person one.  Although both are possible, yet the latter calls for different "prerequisites".  Having an inner connection with the imam and living up to this inner relationship can be considered one of the prerequisites for meeting him in person.