Personal accounts are to be used by the primary owner only. Personal account holders are not permitted to resell, store or give away web-hosting services of their website to other parties. Web hosting services are defined as allowing a separate, third party to host content on the owner's web site.
As long as they only help you with your site, and not get the login details to host their own material, it will be fine. Remember that you, as account owner, is fully responsible for what they do.
