Legal advice on using residential flat for commercial purpose

We have purchased a flat in kondapur area in last couple of weeks ago from builder. Land owner has given hs 600 sgyard land for developement to this builder. So, land owner got 5 flats out of 10 and builder got remaining 5 flats. out of 5 builder flats, one flat is purchased by the relative of land owner, remaining 4 flats of the builder purchased by other people and i am one among them. All flat are registered as residential flat only.Now, the problem is land owner, who owns 5 flats and 1 flat of his relatives plans to give it to ladies hostel but as we 4 flat owner purchased the flats to stay with family and we are not accepting it as it can create lot of problems to live with our family in that hostel environment. We have discussed with land owner but he is not at all accepting our request. We want to oppose this by proceeding legally. Still, apartment welfare is not at all formed and land owner not at all intimated to this before giving his flats to hostel. Can you please guide us how we can proced legally and how much justice can favor us? Thanks