Be carefull during construction about how they are counstructing your building , what type of material they are using , is the material is similar to what they shows etc. Some of the builders are showing good quality of material but using the worst products. Try to get some of the information from the peoples who had given their projects to that company. Do not give a big amount of money in advance. Some of the builders take a big amount of advance and not give attention in your project. So be carefull during any of such deal and always deal with full of your intelligence. Presence of mind is the most nessesery thing during any of the deal.