I was just curious, would google have a problem if a website was selling links with the nofollow attribute.
Why should Google have a problem? The website owner pays the domain registration / hosting fees, so they are free to sell advertising as they wish.
Google will not mind people selling links with "nofollow" in them - besides, isn't Google the one who encourages people to sell links with nofollow?
Google encourages you to use the nofollow attribute when you sell links. They're not trying to be the only advertiser in town, and obviously bringing people to your site - the point of online adverts - means paying for links of some type. Google has a problem when you don't use nofollow on a paid link; they use that as "full disclosure."
There should not be a problem there, it's just the same as selling advertisement space. Remember Google doesn't own your site, you do.