As Kevin has said there are a lot of advantages with SaaS shopping carts.

If you can manage your own server (or have people(s) who can then you should be fine. I could not image from an infrastructure point of view you would build your own physical servers and firewalls, etc... This is why you start out with a VPS from a company like AWS, Godaddy, etc...
Damn, even Digital Ocean has hosting for $5/month.