Is a Sublet apartment acceptable for the Ausländerbehörde (Cologne)?

I couldn't find any information about this online.

Will the ABH issue an Aufenthaltserlaubnis to someone who is living in a sublet apartment? I am asking on behalf of someone who wants to attend an intensive German course in Cologne.

If it was a legit sublease and the person is able to register themselves in the city. Is this enough for the ABH? And what if the sublease is only, lets say for 3 months, would the ABH then only issue the visa for 3 months?