You have to be careful with these offers. Even a solid hosting company like Hostgator, that claims 'unlimited' hosting, is NOT unlimited.
With Hostgator they do have a limit on the total number of files, they call them file handles. I think the limit is 250,000 file handles. While that sounds like a lot, if you are installing a lot of wordress, and they are all at active, you can easily exceed 250,000 file handles.
In addition, entry level accounts are on a shared box and you can overload it very easily. Your users will hate your very slow-responding sites.
So I think the answer is, dont try to get something for nothing. Get good hosting, and find out all the limits, and monitor your sites; if you exceeed your account or your box then upgrade.
And dont believe anyone's ads without more research.