The documents required are:
- Copy of registered sale / conveyance deed through which the seller got the title
- Photo-copies of all earlier sale deed
- Agreement to sell
- Receipt of payments made to seller
- Copy of approved plan of construction
- Title search report
Yes, such deals are considered legally safe.
Before purchasing the property, he should verify from the Registrar of Companies that the property is not mortgaged or otherwise collateral security against any loan etc.
As far as office accommodation purchased in Vikaspuri without the indication whether it is free hold or lease hold is concerned. It is correct that you have paid the mutation charges i.e I think 5% of the purchase price. You can only get it registered if you have got General Power of Attorney having powers to getting the property registered and more so if the property is free hold. If the property is lease hold then without getting the permission of DDA, you can not get it registered. The consent of the builder is necessary if you have not got the General registered Power of Attorney with full powers of doing all the acts as the builder has done personally.