Hello Qasim,
You can go for Arduino Yun as slave device for each house. Arduino Yun has 20 digital I/O, so 10 of them can be used to control relay circuits to control 10 GPOs. Yun has 12 Analog I/O pins of which 10 can be used with ACS712 current sensors to measure power consumption at each GPO. The MODBUS communication with each Arduino board can be done via RS485 for which RS422/RS485 Shield can be used. The master device on Modbus can be a PC or Raspberry Pi 3. Both Arduino Yun and Raspberry Pi 3 are IoT enabled so they can be used to connect with internet either through Wi-Fi or Ethernet cables. Raspberry Pi 3 can be connected to a remote server via Wi-Fi or Ethernet cable to a router and also Modbus protocol can be implemented on it.