Can I have two not neutered male rats together or will they fight? If they become aggresive is it permanent?

I just got them a few days ago from the pet shop I work at. They are not neutered/castrated. They are about 8-10 weeks old. I read on a Rat Information site a href="http://www.quite.co.uk/rats/" rel="nofollow"http://www.quite.co.uk/rats//a that "Male rats occasionally become aggressive towards humans and/or other rats at 4-5 months...He will puff up his fur, hiss and huff at other rats and people, and may attack or bite cage-mates or his owners. He may also scratch at the floor, rub his sides against hard objects (to leave his scent), and leave trails of scent-marking pee wherever he walks...This condition can usually be cured by having the rat castrated, and his hormonal levels and behavior will return to normal after a few weeks." It says it'll cost like $70-$130 to do so for one rat. This is really out of my means at the moment and I hope to avoid it. What I'm wondering is if this aggression will be temporary and only last for a bit. I mean to ask, if my rat(s) do go into this aggressive state, is it permanent or is it just a phase?