Some very general information...

In Vermont (and most places), landlords have a duty to mitigate damages when a tenant leaves early. So in general, they have to make reasonable efforts to re-let the premises upon your leaving. You have to pay your rent until it’s re rented, and that responsibility ends only after they rent it again or a reasonable amount of time passes. Since another person is coming next summer, the rental would have to be short and not on the typical rental cycle.

If it’s a college house, it might be hard to rent it out for the needed time or it might be easy. I don’t know the specifics of course. In short, you’d be on the hook for anywhere from nothing to the remaining rent on the entire lease. If you can find somebody qualified to take over the lease, they’d have to accept the new tenant or forfeit your rent. I’m sure this isn’t what you want to hear, but speaking with a local lawyer is the only way you’ll be able to figure this out for sure.

I don’t know nearly enough about the situation or the local law to give you advice. But the basic rule is that they must reasonably try to replace you with a new tenant. Depending on everything, that could result in you paying nothing, 1 month of rent, or rent on the rest of the lease. Or, 1 full month of rent and then some more per month (for example if the only way they can reasonably get a tenant is if they offer the new lease at a reduced price because it is short-term, so if the new tenant pays 100 less a month you have to pay that difference (and of course that is subject to the reasonability requirement mentioned before, the ll can’t purposefully screw you)). But as I mentioned, I don’t know the local law, Burly could have some specific laws that change this basic rule. Some research would probably answer your question, and a local lawyer would be needed for any sort of assurance.