About service liability by land lord

sir one of my client is took a land for development, and constructed residential flats, out of 40, 20 flats handover to landlord as per agreement. Present developer sold his flats and paid all taxes, now landlord is selling his flats. My question is the land lord has liability to pay service tax or not ? or the builder has liability of service tax on sale of landlord flats ?. In agreement the point not mention. who has liable to pay service tax on sale of land lord flats? please advice me.