This is an actual condo, is under agreement and scheduled to close on March 17th, listed at $625,000.
Possibly the Buyer may be looking to rent a room in the unit, the rent does seem a bit low for it to be the whole apartment.
South Boston rents are generally lower than Boston Proper, so you never know. It's worth a call.
Altho' it's safe to say that the Buyer has no legal right to enter in to a contract for the property until he takes possession, unless it's in the sales agreement to be allowed to show to potential tenants.
Best of luck,