What to charge for rent on a restaurant covered patio?

[Courtney Jackson]

There are a lot of factors to this but I will try to give the reader's digest version. I am trying to figure out how much to charge for a covered patio space at a restaurant.

The restaurant (kitchen, bathrooms, bar, no indoor seating): 1500 sq/ft 

Covered patio: 1000 sq/ft. 

They also have us to around 3000 sq/ft of lawn or outdoor space. 

Since the building doesn't have seating they solely use the covered patio and lawn space for customer seating, as well as the entertainment that plays. The tenant was supposed to buy the property but couldn't make that work so it went back on the market leading to us purchasing. The low rent of $1800/mo was given because within 30 days they were supposed to purchase. 

Typically a patio wouldn't necessarily be an extra cost for tenants, but in this case the outdoor seating and lawn space is major part of their business. We are in a small town, but typical commercial rent in this area is around $1.5 sq ft per month. 

Any advice on how to approach figuring the rent in this situation would be greatly appreciated. Thank you so much!