I am somewhat new to Office 365 and in particular, Sharepoint online.  I have seen how to setup a public site and a team site but I was hoping to setup something that I fear Sharepoint online will not allow.

My small business has a number of projects for different clients going on at any particular time.  We use BaseCamp.com, an online project management service that (for my plan) allows a maximum number of projects and a maximum total space.  I can give any number of people access to a project, files can be uploaded and downloaded, messages can be distributed and to-do lists can be managed.

Since most of our projects come to an end, I can always archive or delete a project, making room for new ones.  I had hoped that a Sharepoint Online solution could be made to replace BaseCamp but it seems that if I want, for example, to setup a file sharing/message sharing portal and give my clients, employees and contractors private login capabilities in Sharepoint Online, all of them will require an Office 365 account in order to participate.  Am I right?  If so, as I suspect, a SharePoint Online solution to this business requirement does not fit well.

I think that the same thing goes for Lync, which I had initially hoped would allow me to replace my GotoMeeting account.  With GotoMeeting, a client or prospect could call me, asking whether I might be able to help with a problem.  I start a meeting, give them a URL and quickly enough, they can see my desktop or, if they want, I can work on theirs.  It seems to me that Lync has this basic capability but assumes a business model where I can only collaborate with other Office 365 subscribers, again, making it a poor fit for my particular business model.  Please let me know if I am wrong about this.  I am new to this.

Any guidance would be appreciated.