How necessary is a pantry for fulltiming?

You don't need a space for food storage that was designed for that purpose, even though it is handy. Any area will work...under the sink, in the space under the dinette (if there is one) or even in a bedroom closet. I think you'll find that keeping a ton of staples on board simply isn't necessary. Why carry around hundreds of pounds of groceries when there are stores everywhere?! A week to 10 days worth of staple items is enough.