If you only want your friend, just port forward and host from home.
If you want more people, you will need a proper server.
I would recommend getting a VPS.
Well, that usually costs money. Really, if your network protocol is good, you can host from home. A decent MORPG should only take around half a kilobyte per second, maybe even less. Its all about how you control the packets you're sending.
But then again, even getting DOSed at home(by bad people) isn't really good idea.
A VPS these days isn't that expensive, especially if it's just an experiment and you don't need a lot of resources. Hosting at home is bad.
You can get DDoS.
You can't turn off your computer or router.
You'll get complaints when it's down.