As long as you're not the host and you're in a co-op game, you should be getting 10 gold every five minutes, which goes towards the 1000 gold you need to attain the "We can be heroes" achievement. You don't actually need to play with anyone. You can do this with two controllers and a dummy throw-away gamertag to act as the host. Just create a separate gamertag, start a character on it, and as soon as you're able have your main character join their game. Now it's a waiting game. I recommend putting a rubber band on the left analog stick and walking into a wall forever (to prevent the 360 from going on standby.)By the way (and I'm going off-topic here), does anyone know how to get "henchmen wages"? I need to get that achievement and a couple others before my Xbox Live runs out but I can't figure out how to do it. If you know how to do it and are willing to let me get it, let me know via a PM.
You'll get it eventually. Set it all up and then go watch some TV or eat a sandwich.