There may be a couple of approaches to your question. Without seeing the facility and design, it is possible only to estimate a rental value of 5% of the annual cost. It is probably worth between $5 to $15 per square foot without a concrete floor, but it could be worth less if it is old and worth more if there is added concrete, etc.
The other approach would be to charge a $0.40 per head per day yardage fee. This is what is done at feed yards. The yardage fee is to cover lot/buildings, electricity, water, etc.