Council may, after notice to the owner and after holding a public hearing thereon, condemn an unsafe structure by giving notice to the owner of the land upon which such structure is located, specifying in what respects the structure is a public nuisance and requiring such owner to alter, repair, tear down or remove the same within such reasonable time, not exceeding sixty days, as may be necessary to do or have done the work required by the notice. The notice may also provide a reasonable time within which such work shall be commenced.