Because we were looking at smaller town colleges where renting small units comes cheaper than on campus housing, especially when we would most likely have two boys in college at the same time. Plus, assuming they'd have a job while at school, I would think they'd stay there 12 months and not just 9 months if they want to still have their jobs when they come back, not to mention if they are taking summer classes, summer housing on campus is usually more expensive (or was when I was in college).
But as I mention before, in our case there's a big issue with food (and other allergies) so living off campus would also be more practical and safer.
Plus, depending on the location, we might consider purchasing a small property and instead of renting we'd be paying mortgage and keep the property as a rental once we wouldn't need it for our kids anymore. Wouldn't be the first parents doing it this way. At least we would see our money going towards something we would still benefit from.
You did say your boys are 3 & 5 right??? And you are looking at possible colleges for them now? How do you know a "smaller town college" will be right for them? They might not both get in to the same location. They might not want the same things. My son is a H.S. freshman, 14 almost 15 and he has NO idea what he wants to do or where he wants to go to school yet. And despite being gifted, isn't getting the best grades at the minute so who knows where he will get in. My older DD19 is at a small liberal arts school in a large city across the country. (I just sent her back yesterday) All I do know is my son won't end up where his sister is because it wouldn't fit his needs.
Slow down, while trying to plan for the cost of college is a great idea. I wouldn't hurry to decide that both kids will go to the same small college. Plus colleges may change drastically in the next 12 years. What is best for either child may be totally different from each other. One might need to go to college early, the other need a gap year or two. At 18 they will be adults, and while we as adults can say "this is what I will pay for" they don't always do what is expected.