You can not host another person's web site under your account. This is spelled out in the Terms of Service and Acceptable Use Policy. All sites under your account must be "yours", and you can't subhost, sell, trade, or give away LP resources to someone else. If you can't justify the new site as "yours", you'll have to buy a new account in order to host it.

I do not speak officially for Lunarpages (I am a customer), but that's my understanding of the rules.