The rules state that non-limited building can be produced as long as there is a place in the city outskirts to put them.

Does this mean that you can put as many markets or granaries as you´d like in the outskirts of the same city or is there an implied limitation of 1 market/granary/etc attached to each city?

You can do as many as you like, terrain permitting.

You can have 2+ granaries around the same city? Wow, I need to re-read that section.