When i owned a 2 flat my renters always had access to to breaker box in case I wasn't around to reset it for them. By right's you should have access to the electrical box in case something trips, or happens so you are able to reset the breaker.. Ask him what happens if he is not around if the a/c should trip the breaker will he always be around to reset it, plus @panzrwagn is correct it is the law to have access, unless he dosen't have it up to code and dosen't want to show it to you..I am reaching here but.... contacting the city inspector to verify your rights
is not a bad idea hope this helps