This guy! I have been interested in bats since the first time I heard of him.
My recommendation is to recommend that it be evaluated and removed by a professional. There’s a lot more to having bat’s than just the bats themselves. The guano is a major health concern and there are insects that eat the guano. The insects have to be dealt with as well. It is a very expensive project. I once found bats in an attic and reported that they were there. My customer called me later to tell me that the cost for remediation was $18,000.00. It turned out that there was a “colony”" and there were thousands of bats (creepy right). Just closing them out does not remediate the guano.
Your customer probably got bent over and “bat screwed” for 18K. Seems a bit much for a bat remediation.
I actually built a couple of bat houses and put them in trees around my lake to keep down the mosquitoes. We have noticed a big reduction in the bugs with the bats around.
I inspected this old church back in 2008, surprised I was able to find the report, but this was the worst bat infestation I’d ever run across. Piles of guano everywhere, I looked up and there were hundreds of bats up at the ridge, it was mid-morning so most were probably asleep but a few were up there flying around. One of those rare experiences for sure. Sorry for the poor quality pictures.
Maybe, I’m not a bat remediation expert but they got three estimates and that was the one in the middle price wise. They had to cut out ceilings and walls to get to all of them.
I can see that now. Years of infestation can be big $$ if it’s never noticed. 18k is years on unnoticed/ ignored bat issues. Guess some folks should hire someone for a yearly check…Could save them some money. 
That is pretty incredible. Beautiful old church otherwise!
My first day in Agronomy 101, the prof asked us to answer “What is a weed?” The answer is “A plant that is not where you want it.”
Ditto pests. Bats living where they aren’t annoying us (running across the attic floor), or creating a damaging or health issue, (piles of guano in our attics) are not pests. When they are living in our attic, they are pests.
I ran into a situation in Virginia where the bats, and droppings were in the bell tower. It was so bad that the ceilings in the front entrance was bulging, and the smell was terrible. They wanted the situation remediated. It was in July. I told them we cant do anything till mid September because the young ones and they are protected by law. Once the young ones are weened from their mothers then we can exclude them from the tower. They didn’t like that and said they would get an exception. They never did and had to wait till September. If you look at the droppings it is insect parts. Never disturb the droppings unless you wet it down, or use a vacuum with a hepa filter.