I really enjoy career mode for most of the reasons stated above. Hacking together three semi-similar contracts to find what I actually want to do is half the challenge. All my Minmus and Mun exploration came from tourism or research missions. Rescue contracts gained me all my kerbals, station missions were combined with satellite launches, rescue missions and goodness knows what else. Each of my stations includes a small shuttle for collecting lost Kerbals which means I can gather them up as they appear and then just do a single return mission, usually backed onto a science or passenger run. A seven Kerbal craft is not much more expensive than a 3 Kerbal craft and can easily swing past a Munar / Minmusian station on it's way.
By the time I was ready for Duna I had funds of about 6m just sitting about which let me launch missions to Dres (2 launches, 8 kerbals and about 2.5m spent), Duna (3 launches 8 kerbals and about 3.2m spent), Eve and Eeloo (1 launch each, no kerbals but a small 3 kerbal station and shuttle craft to support any manned missions I might send later). These all included a return ship and a large, nuclear engined "Transfer Tug" which is basically a 3.5m unit with a 2.5m docking port at one end, nuclear power at the other and fuel sandwiched in between. New launches to these planets now will be lighter as they will shuttle between there and Kerbin to just pick up any 2.5m modules I feel those missions require.
Making every launch count for multiple missions helps, add in the ability to reuse parts of a mission that would otherwise be discarded and you can get even more out of them. Yes, I accept it might make the missions slightly more expensive to launch initially but the payback comes in time when each follow on launch is cheaper.
Also make sure you have the strategy that gives you cash for reputation is running in the Admin block. This will help a lot early on when rep is dropping into your lap just for being awesome and Kerbal.
I have never felt like i was struggling for money except right at the start to do the initial expansion of my facilities. After that it just came rolling in.