I foresee a slew of folks pointing the fingers and saying "I told you so" on many angles and opinions...
I wonder: isn't there in the lease contract a break clause with a hefty penalty proportional to the length of time remaining on the contract? All things aside, that could easily offset the moving expenses - not the mental breakdown, though.
I don't know the rules around here in the US - it varies from state to state and maybe even from city to city.
Perhaps bring the new/prospective owner to the bargaining table would help?
I once had to deal with this and the owner sent a letter saying the property was being offered for sale, gave us priority to buy it or leave within 60 days. Obviously that, without cash, we were forced to leave but fortunately the law didn't match the owner's planned schedule for his own sale plans: we had 30 days to reply, then 90 days more to vacate the premises (this was in Brasil). Also, the lease contract had a break clause with a hefty penalty to cover the moving expenses. In the end we left the property within 60 days but we got lots of extra benefits from the owner for the expedited process, such as one month free and paid moving expenses (on top of the break penalty).