If your documents are still in your male name, then don't bother disclosing anything to your landlord and keep all records in your legal name, but change them when the time is appropriate. I doubt they'll make a fuss if you start going in girl mode, and if anyone asks just tell them you're making some changes. They don't need to know any of the details, that's your personal business, not their's.
As long as your a good tenant, pay your rent on time, and mind your neighbors, I really doubt the landlord will care. But once you go full-time and change your records, if they do make a fuss, you can always find a new apartment.