It could help to support the libraries, I guess some people would even pay an "extra" because it's in there.
Leave the cameras on, lock the librarian's office and password-protect the computers after hours, and require the tenants to return [or check out] any borrowed material by the next morning. Realistically, you'll probably have one or two bad tenants over the next few decades who leave their trash inside the library or try to steal the crappy old library computers and it will mostly be fine.
It doesn't even have to be below market rate: They could pair it up with a grant program where someone else is picking up the market rate rent (or the difference between market rate and what would make it attractive for scholars) for the "in residence" person.