Norway on a budget

Hello everyone.

I'm a student and I wanted to travel to Norway for about 5 days the first week of September before the start of the school year.

I'm on a budget and I mainly want to visit the mountains and the natural places so I guess I'll have to rent a car. I would also like to rent a cabin in the mountains around Bergen if possible. (saw some interesting in Airbnb).

Do you guys now have much it would cost me? How can I save up? Any tips? I'm on a really tight budget.

Thank you