Thunderbird Bullet 2004 model
Well, the bike has became quite old as it would have been used for last 12 years, which in turn means it would definitely have some flaws in its overall condition. First, you should go through basic visual inspection like body paint quality, tyre conditions, condition of the screws and the engine noise. The engine was a gem of its time and if found in perfect health, it can still thump for 12 more years without a problem. You can take a Royal Enfield mechanic along with you as they can judge the quality of the engine by simply hearing its sound and the amount of oil found leaking from the spaces.