You can, but if they know that you're doing incalls there, typically either the price goes up or they want some freebies. Or both. So if you're going to tell them anything, use a cover story.
Realistically, if you pay the money on time and don't trash the place, most landlords won't care, so why tell them? About the only exception is if this is somewhere they want to live again, when they can be concerned about what the neighbours think. But as one of the basic rules of sex work is 'don't annoy the neighbours', that shouldn't be a problem either.