Ideas to install door on Pole Barn on rental property

[Scott Passman]

I recently acquired a property that has a structurally sound pole barn in the back. Looking to rent it out as storage for additional income, but I need to secure it with doors first so it can be locked. The size of the opening is roughly 8.5' x 16'. Any ideas on the most cost effective ways to either self-install or hire out an installation of this door? Thoughts on the best materials to use?