Dear sir,
As per the GST Act, you may have two registration since, different nature of activity, these will be treated as establishment of distinct persons for the purposes of CGST Actsec 25(5).
Whereas for the turnover calculation the threshold limit of rs. 20 lakhs(other than special category states) as follows.
Supply of Goods or services or both if your aggregate turnover in a financial year exceeds rs. 20 lakhs to get register under sec 22(1) of CGST Act.
If rent and trading of business turnover not exceeds rs. 20 lakhs individually in a financial year and registered as business verticals, but your aggregate turnover exceeds the above limit, then you have to get register yourself.
Note: if the rent against residential dwellers, then it is not covered under the GST regime.