Solly
If the radio is connected to the ESC then it has a BEC (battery eliminator circuit) built in which provides a regulated 5V (or 6) supply to power both the radio and the servos.
However if you are driving 7x9g servos I have my doubts whether the BEC in the ESC will be powerful enough.
The fact that the previous own managed to burn 5 servo is a bit of a worry but suggests he was not using the BEC in the ESC at all but powering radio and servos from a separate power supply, either a dedicated high power UBEC or a separate battery.