Nastase G. Eduard:
I'm researching more on Raspberry and I see its way cheaper to run a relay this way. Won't cost me more the 100ε for a relay that will be self-sustaining. Considering there won't be any monthly expenses (except the internet) the initial investment can be recovered, 24/7 relay and no electricity cost, perfect!
I don't know if someone else already tried that, but you could use a BeagleBone Black [0] as well. It's a bit more powerful (1 GHz, newer ARM processor generation) than the Pi. The advantage I see is that it's blob free, which is a concern with the Pi for some people (please correct me if I'm wrong!).
[0] http://beagleboard.org/Products/BeagleBone%20Black [1] https://lwn.net/Articles/576434/