I would think twice about purchasing this TT. If it has, as you say, a serious crack in the roof there will be serious water damage somewhere on the inside. Fixing the crack in the roof may be to late, the horse may have already got out of the barn (so to speak), the damage may already be done.
2014 Palomino Puma 25RS
2011 F-150 Super Crew XLT
Days camped in 2014 - 23 Camped 2015-47
Camped 2016-71, 2017-33, 2018-29 booked