Gst on rental income

A small retail businessman having net turnover of about 15 lpa had been registered under vat. with GST roll out making the exemption limit as 20 lakh gstin number was not required. all of a sudden the demise of a family member caused a transfer of property according to the will of the deceased with rental income of 5 lakh per annum in the name of the businessman. is he now required to apply for GST on rent as well as business or turnover in business is different from turn over in rental income.