I have a query about the process for getting Niederlassungserlaubnis. I have been in Germany for over 3 years with a Blue card and am eligible to apply for Niederlassungserlaubnis. The Munich Auslanderbehorde website (http://www.muenchen.de/rathaus/Stadtverwaltung/Kreisverwaltungsreferat/Auslaenderwesen/Unbefristeter-Aufenthaltstitel.html) says that I need to show a rental/buy contract with size of apartment:

"Mietvertrag oder Kaufvertrag mit Angabe der Wohnungsgröße (Quadratmeterzahl)"

However, my contract (which is a regular rental contract) does not mention the apartment size. Can anyone who has gone through this process confirm if apartment size is really required? If yes, then can I get a letter from the landlord confirming the size or do I need to get a new contract signed?

When my wife was applying for her spouse reunification visa she was asked specifically for a contract mentioning the size of the apartment, or if the contract didn't mention the size of the apartment, a letter from the landlord stating the size was acceptable as well. So I am guessing if they explicitly mention that the want the size of the apartment I suggest organising a letter from your landlord stating the same. 

In my point of view for NE application they only need Rental contract. However, even if in some city they ask for details then an apartment size of 12 Sq. m per person is considered fine.

Please do confirm from office in your city !

Good Luck !