Query on Duplex House Purchase in Aligarh (U.P.)

Dear Sir, I am interested in a Duplex house constructed inside a layout of 65 Duplex houses which is approved by ADA (Aligarh Development Authority) as per builder. They have kept a play area , community hall and 9 FT road b/w two rows as per ADA instruction. They have formed two companies (Nav Nirmaan Company and Dream City Company). Where Nav Nirmaan deals with land purchase only and the Dram City is only for builder contract. Now when it comes to commercial, they are asking customer to get it Register LAND only at the time of purchase not the Duplex House, and that land registration cost is nearly 1.25 lacs only. Now My Question is -> Since house is already constructed inside the layout, and they are costing duplex rate nearly 50 lacs, So i am doubting on the land registration only when house is already constructed at the site, is that legal to purchase such property where the land is only registered and the house is not? Please note: When i have insisted to get it registered both the LAND and HOUSE at the time of purchase, so they are not in the same agreement, and asking me to do it later after the Possession . Kindly advise, if the deal is fear? My Email ID - [deleted] Thanks