Sharepoint 2013 Intranet and Extranet Topology - How?

I am currently trying to decide on a Sharepoint Farm Topology.

Currently (in terms of our needs), I think a simple three tier topology will work.

i.e.

Web Front-End Server Application Server Database server

To start with our primary aim will be to use SharePoint as a Intranet. However, on our roadmap we would like to extend some elements of this - as an Extranet with some coustomers.

Should we go with an Extranet option in the future, so do we just (in simple terms) create a new web application in Sharepoint 2013 on the existing web front end, sort out a host header and SSL and a means to manage permissions.

Or could we create a new front-end server, which is only houses a new web application (the Extranet) - but still uses the same Application and Database server (as it will be potentially sharing the some of the same content databases)?

I am primarily a C# Web Developer - which is typically how I view most things. As I am learning - in the world of SharePoint nothing is simple!