If you look in the faqs you'll find a section titled Publishing Rules & Policy.
I believe that rules 13 and 22 under this section apply to your question.
Basically you simply have to own the content or have permission from the person who does own it in order to use it. Additionally it can not be content that is duplicating something that appears somewhere else on the internet.
The language in the faqs page states that your hubs will be moderated for these infractions. This suggests that individual hub articles will be taken down not your account.
Honestly though, if you're spending four hours every day writing hubs you have no reason to buy them from other sources.