There are basically no eligibility criterial for initiation. Any person, of any religion or belief system, whether being initiated for the first time or an initiate from a different system, is welcome. One has to start from where one is today.
Shri Shibendu says “Anyone who wants to learn Kriya Yoga with full respect to the traditions of Satyalok is welcome. If one has taken a dip in the holy ganga river at Haridwar, will he not take a dip at Gangotri, its source?”