@John2654
As far as I can remember, all short term rental income is now taxable, even a bedsit in your own home.
I did my tax return yesterday, I believe you would need to file it under domestic holiday home rental and fill in and file the 1019 form for holiday rental "utenom næring". You are only taxable for the net amount, so make sure you deduct all relevant expenses like electricity, insurance, rubbish collection, property tax etc. but only for the period it has actually been rented.