I started out pen turning with a Taig in 2004, which is basically like a Sherline. Sherlines had a bit more options. That probably is a very good price depending on what comes with it. I lived overseas, couldn't find an affordable and quality lathe so I bought a Taig and took it back overseas in my suitcase. There are some limits on them but for the basics and segments and even kitless pens - they are possible with a Sherline/Taig.
With the 4000, you will need to look for a tool rest and other options for wood turning. I don't remember what all I purchased with it but it was about $200 in extras to get to pen turning.