What is a product ID in USB and do I need to buy it for my project?
I am not sure what exactly you want to make, but if it is a host device you indeed don't need an USB VID/PID. 

The USB VID/PID of a slave device is used by the host to identify the driver(s) to be used for the slave device. A host device does not need to identify itself to the slave, hence it does not need a VID/PID.