Buying a part of property which is not divided what is legal procedure

Hello Sir/Madam One of the builder in chennai is selling his land which is about 1200 sq ft. The land is part of the land which is of extent 3000 sq ft where the land lord wish to sell it partly out of it. The land lord says that he did not subdivide the land; but asks me to register and then sub divide... He also says that the land is having the approval for building My question is, whether can we but a plot which isn't subdivide and then subdivide later after purchase ? Is that advisable or will there be any problem in future.