A secondary residence—I'd prefer to use the term covert accommodation—could be used, whether it's a hotel room that's purchased under a covert identity or whether it's an apartment that's rented under a covert identity. It's a covert place to meet, removed from the police, where you have to meet with this person to coach them along, and to give them the support that's necessary.
It's the separation between your professional life and your personal life, and the separation within your professional life between what you actually do and the identity of the organization you're doing it on behalf of.