Just a random question, what happens when you don't have a single silver piece and you don't have a single item of food? Does your money go into negatives? Do your pets not get fed and starve? What happens?

Nothing happens, other than you don't have any money. It also doesn't go into negatives, just stays at zero until you can gain it back. I think your pets should continue to regenerate energy and you'd still be able to use them as usual, too. The only penalty is having no money. 

Fun fact: it was originally planned that the game would start sending your pets to the Pound if you didn't keep them fed properly, but this feature was never implemented due to negative feedback. You can read the thread on it here if you're interested. 

Haha cool thanks for answering!