What's the cheapest way to set up this business idea?

I want to try a simple business idea that combines the following:

• Storefront for merchandise: membership card (sort of a novelty license), t-shirts, buttons, stickers
  • Charging, shipping, inventory
• Twitter & Facebook feed with regular content (I know how to do this part :p)
• Email signup w/ special offer, i.e. sticker (needs to tie into shipping/inventory)
• Auto-email digest of top tweets every week

I have done most of this before, but what I'm curious about is the best, cheapest way to set up an easily extensible shop. I have never tried selling merchandise before so I'm not familiar with the landscape—presumably there are services that will manage it for you completely, but I'd be wary of the $$$. I have like no storage space in my NYC apt AND a full-time job so not sure how I would do inventory and shipping from home, unless maybe my wife wanted to help as a kind of part-time "job"...

So far it's looking like FOSS shop framework on AWS + Mailchimp + something like Buffer, but I'm open to other ideas (like serverless with AWS lambda?)

Thanks for your ideas!