I have five boys that are still intact, they're about 7 months old now and have been living together fine for the last 6 and a bit months. They have the odd disagreement, but they're fine, nobody gets injured.
However, I went away for a weekend recently and left them in the care of my dad, who has three females. I came back and a couple have one or two scabs, but nothing major. The females being close caused them to get a little hormonal, but it's all good now.
It's possible, and it will have very much to do with the individual personalities of the rats.
Most people have more than one rat, and if you decide on male rats and don't neuter them, you will end up having at least two male intact rats. I have two, and they have tiny skirmishes but are good mates overall. It's far preferable to having one rat; they need the company! So my answer is, of course yes, unless you're super unlucky and end up with some abnormal aggression situation. Some homonal aggression is normal when they're five months or so, but it's usually not so serious that neutering is required.
I currently have four boys. My first rat - Alfie I adopted from his previous owner. He'd been by himself for many months, and it was four more months with me before I was able to get him some buddies. I got two 4 or 5 week old boys, and there have been no issues between the three boys, alfie absolutely loves them.
This past Friday I introduced a 10 week old boy who was very much the dominant rat in his old mischief, and there has been some bloodshed over the past weekend while I did intros.
So, in order of age:
Alfie - 1.5 years roughly
Fergus - 10 weeks (newly introduced)
Ryker - about 8-9 weeks now
Houdini - Same