Thanks for the quick reply to our question. However, since we didn't formulate it correctly, we didn't get the answer we were looking for. So here we go again.
Can the word "period" stand alone without any form of postmodifyer like eg "of time"?
Is the sentence "Apartments for rent for a longer period" grammatically incorrecy.
We hope to hear from you soon.
Christine and Trine
In short, no. Use time rather than period there.