Proprietor with 3 business units

My client a is doing business in proprietorship form . He has 3 business units with annual turnover of 8 lakhs . All the 3 are services namely service of computer, tent house and rent of property.  He took gst for computer service as the clients asked for gst Bill . Does he have to pay gst on all the 3 businesses ? Does he have to show all the 3 business income in his annual return ? Trade name of computer service is shown on gst certificate.  Please suggest .