How legal is operating a Tor node?
I'm thinking of putting up a machine (and a VPS) to just run a node.
I just don't want to get into legal trouble for running a(n exit) node.
Running an exit node may be a different story. You could get false DMCA takedown notices or get charged with someone else's crime. Think of it this way; you're running an open proxy. Uses of Tor can send any traffic through your connection. That being said, some ISPs are ok with it, others won't tolerate it.
I suggest you checkout https://blog.torproject.org/running-exit-node if your really serious about running an exit node.
But you could use an anon currency-exchange or currency-bridge like paysafecard.com to obtain some value and obtain bitcoin with that value and never use that bitcoin key again to avoid that.
If not there should be. You send X amount of bitcoins to a middle man who then gives you X amount back. Technically they will be different coins and they'll go to a different account #, so you can't trace anything.
(IANAL, may not be legal in all countries)