The answers to those are entirely variable. There is a certain degree of natural talent that one is simply born with, yes; however, most magic is generally founded more upon learning and developed skill than innate talent (innate being an obvious exception) . Whether a sort of contract is required or not largely depends on the level of consciousness of the source. If the source is an intelligent, eldritch being, some sort of pact is almost invariably used; if the source is simply pulling from natural ley lines, it rarely is, although ceremonial bonding rituals to attune to the force are still common. Mages [i]can[/i] simply pull said power without permission... however, that rarely works well and if the source fights the pull, it affects the quality of the energy (nevermind possible retribution) . And such contracts often bolster the mage's casting, anyways, by being supported by said magical source or entity.

Nailbrain is hilarious. Just change Castle Town to Castle City and he is good to go!