how hard is a purebread collie's coat to maintain?
What kind of daily maintenance would need to be done?

For a Rough Collie (like Lassie), daily brushing is ideal, while weekly brushing should be adequate. They tend to have mats behind the ears, in the armpits and britches area and on the tail.

Agreeing with OperaChick. And you have to learn to line brush; lifting the coat and brushing it down in sections, so you're getting all the way to the skin. Too often we see dogs that are perfectly brushed on the surface, but with packed, matted undercoat next to the skin.

I agree with OperaChick and Vetgroomer, especially with separating the layers of hair and brushing down to the skin.

I don't have Collies, but I have Shelties and both breeds have the same kind of coats. I brush them every day and use combs and brushes.

If they get wet from being outside in the rain/snow, rub them good with a towel, then brush, otherwise the hair will mat in places (tail, butt cheeks, ears) and getting the matted hair out is not easy.

In between baths, I use a spray bottle with diluted unscented conditioner and spritz it on a terrycloth towel, then rub it over the coat/paws to remove light dirt. But they stay pretty clean with that and the daily brushing, which I can't emphasis enough.