If the theatre is closed and the landlord owns the equipment, then the business is worth nothing. The only value to the owner is the rent that can be collected, and he should be satisfied with a rental figure that covers the mortgage if there is one, taxes, insurance, and whatever maintenance he agrees to cover, and a 10% profit margin.
If the theatre is operating by a tenant with a lease and is profitable, then the tenant could expect to recover the value of any equipment he owns, plus up to two years average profits. According to a theatre management book written some years ago: "Regardless of exceptional conditions or favorable lease, no theatre business is worth more than four times the average profit per year, computed on a five year basis." Based on that calculation, the theatre you are interested in would have had to average about $24,000 in annual profits over the past five years. If the current tenant still has x number of years left in the lease the question becomes why does he want out? It could be due to health, retirement, or a number of other reasons, but regardless you need to see the books (both sets) to determine that he isn't just trying to dump a losing venture. If that is the case then the business has no value for him as well except for the value of the equipment that he owns. Acquire box office figures from the distributors as well as from the operator and compare. Find out how many years are left on the lease. You need the present tenant to show you his tax records to prove his profits for recent years.
By the way, who is selling the business... the owner of the real estate or a tenant?
All the theatres that I have leased over the years, I never paid a nickel for the business, only for equipment and that was only at the one in a large mall. At every small town theatre the landlord always owned the equipment, and it was a situation where the lease had run out and the previous tenant had no interest to continue.