When a building is sold, the new owner of the building takes it subject to any previous lease, so no, you don't have to sign a new lease. You might want to however, to assure your security deposit has been properly credited, or if you get better terms, or even equal terms as it may well extend the lease period. That assumes that you want the lease to stay in effect, something that seems doubtful here given the financial constraints that are facing you and your roommates.
A proper response would require a thorough investigation into the history and background of this relationship. The information provided above is just that, information, to be used as you see fit.
While I cannot giv e you legal advice in this forum, as a general matter you do not need to sign a new lease simply because the building is sold. You can stay there to the end of your tenancy under the existing lease. However, you should review your lease carefully to make sure there is no provision to the contrary.
THIS RESPONSE IS INTENDED TO CONVEY GENERAL INFORMATION ONLY. IT SHOULD NOT BE RELIED UPON OR TAKEN AS LEGAL ADVICE. FURTHER, THIS RESPONSE IS NOT INTENDED TO AND DOES NOT CREATE AN ATTORNEY-CLIENT RELATIONSHIP.