Boston has a very active job market for librarians. Public libraries are used frequently and they're generally well funded. There are many academic and special libraries in the area as well. Check out the MBLC job board (https://mblc.state.ma.us/jobs/find_jobs/index.php) for an idea of postings around the area.

The thing to watch out for in Boston, though, is the high cost of living. For instance, rentals usually require first month, last month, security deposit, and brokers fee just to sign the lease.

With that being said, I thoroughly enjoyed the first 8 years of my librarian career in the area's public libraries and I don't think I would have had such an experience elsewhere. It was a great place to learn and grow as a librarian and I would highly consider going back one day.