I also think there should be different ways of getting money other than contracts, and I do like the idea of selling stuff you mine from other planets. You could also have a "Space Tourism" type of industry, where kerbals pay to be taken to specific places for an amount of time. For example, they could request to be sent to Duna for a year, or any other planet. If you had a ship specified as a space station or base from the rename menu, they could pay to go there instead. You could get these missions the same way you would get any other contract, probably after completing the explore mission for that body. However, if you make them return too early or too late, or they don't get to their destination soon enough, you would lose some money and a large amount of reputation. You'd also have to have a large amount of reputation to unlock these contracts in the first place, because who would want to go the a space station from some random little space centre in the middle of nowhere?