[brudgers]

Easements are a form of encumbrance upon a title. Though real estate law varies by state in the US, access easements are typically the only form of easement established by use...i.e. Passage across the property for physical access to another property. Any other easement must typically be recorded.

Recording an easement requires paperwork at the courthouse, doc stamps, and approval of any lien holders (such as a mortgager). The reason is that the lien holder has a secured interest in the property secured by the title - that they have joint ownership is the easiest way to think about it.

But rest assured, that if you build a fence on your neighbors side of the line its his fence. You can have a contract that gives you the right to access it and prohibits your neighbor from demolishing it, but it's with your neighbor as an individual. If they sell the property the new owner owns the fence and is not bound by the contract.