As far as expenses go, you can get a VPS for a few dollars a month, or even as cheap as $10 a year, which would be adequate for a bridge, but for a normal relay, you'd want something bigger. That can cost anywhere from $5 a month for a small VPS to hundreds of dollars a month for a dedicated server with unmetered bandwidth. I think any little bit helps the Tor network, though. I'll post a tutorial on how to setup a relay, probably tomorrow. It will be *almost* copy-paste easy, but you'll have to change some things for your specific server, like the bandwidth limits.