Been running a relay at home for about 3-4 months now and like other poster barely notice the traffic. IIRC recommended upstream bandwidth is 2Mpbs or greater, if you run a relay on a connection without enough bandwidth (in either direction) it's not really helping the network, (Roger sez!). Sorry don't have a reference link handy for this factoid. Also make sure the connection is stable.
Thanks for that! So my 5Mbit estimate is already more than enough, good to know.
Yes, as every documentation and tutorial I found also mentions this, being an exit relay seems to be default. Thanks again for pointing that out.