I have absolutely no experience with this, but will give it a try. The only comparable situation I have dealt with was when we rented offices to a totally non-affiliated insurance agency. They had their own separate entrance and the adjoining door to our lobby was kept locked at all times. I would think that a phone call to your regulator would be in order. It does not need to appear that you have any sort of referral business with this realtor - make sure the rent is a comparable market rate.
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"Once you learn to read, you will be forever free."
- Frederick Douglass
My Opinion Only.