THANK YOU TO EVERYBODY!!!
Yess, I was looking for:
USB EXTENDER. It is an amplifier that boosts usb signal to usb port through RJ45 cable.
This solution is expensive for usb2.0, less expensive for usb1.0. I'd use a cat6 cable. From 30-40 euros to 250-350.
But it is clean and transparent.
USB OVER IP is a microcontroller, like a small computer that takes usb signal and envelopes it under a TCP/IP protocol. It is only one element, the other element is a software, unwrapping things inside your PC. It is less clean and less transparent. Costs may vary, from 100 to 350 euros.
I'm still thinking I'd better to throw in a pair of old laptops.
But a won a cheap auction of a dlink usb-over tcp/ip to give it a try!