On a forgecraft based server there were jobs where you could chose 2 jobs out of like 10 or so and if you chose miner and you mined stone, ores and you got money and if you were a farmer you would get cash for farming and so on. I think this would be the best way to get cash for the claim area blocks. In addition we would have a money system and could setup player shops. Just an idea because i thought it was a pretty neat system. Also if we could have a battle arena for ars magica 2 and thaumcraft 4 battles at spawn it would be a lot of fun. Gl with sorting out all the server side stuff.
p.s. if you need help with building spawn and so on i think i'm a pretty good builder so i could help with that