Dear Sir,
Service tax is applicable on you if your rental income during an year exceeds INR 10 lacs which I am sure the case is.
Further, as Far as GST is concerned, it will not be applicable until 31.03.2017. Government is trying to put it in place from 1.04.2017. However to is it seems very difficult. We anticipate it somewhere in October 2017.
Please feel free to call/ revert in case of any doubts.
Thanks and Regards
Abhishek Dugar
CA CS B.Com