Fenced yes but I want it doubled with hot wire since it is bob wire. My BIL wants to fence off 4 acres for them right now. Barn? We are arguing about that right now. I would rather take my time and have things perfect. DH doesn't want to throw away more money and wants me to make it work within a month. He says what I have there I have here minus the hot wire.
Does that mean there is a barn or isn't one? Where would you store feed and supplies out there? You should go out there and take pictures. How far is it? Would you eventually move there for the short term too, or just keep horses there...
Is your BIL a horseman with skills already or is he new to it?
I'd definately put up hot wire to start, and over time replace the barbed wire with more hot wire and/or field fence of some kind... and use the heavy gauge stuff too.
You don't need a barn right now, and hot wire is cheap. Just buy enough to run one strand at the top of the barbed wire, and a solar charger for right now.