I was part owner in a Twin Comanche for a few years. This one was in great shape before I bought in to it, and we maintained it very well. The Twin Comanche is one of the most economical twins to run, in my opinion. 155 to 165 knots on 15 to 17.5 GPH.
We figured total operating cost (including maintenance, fuel, hanger, insurance, engine and prop reserve, oil changes, and annual inspections) worked out to about $120.00 per hour (as of 2002). Fuel has gone up since then, though.
I was lucky enough to have bought into a solid, well maintained plane. If you buy one that needs "a little work", you can easily drop $20,000 or more before you know it. Even with no suprises and taking care of problems as they came along, it was not unusual to have annual inspections cost $5,000 or more.
My advice, if you decide to buy, is to make sure you put a bunch of money aside upfront for contingencies, and replenish that kitty every time you fly. Charge yourself an extra $30 an hour or more for the "suprise" fund because you will need it.
And remember that it's a buyer's market right now. Which is great if you're buying, but not nearly so great if you try to sell in a few years. Who knows when the market will turn around on twins, if ever.
What I've typically seen is that you are better off buying if you are going to keep the plane for four or five years or more. Typically you spend the first two years spending a ton of money fixing what the last owner deferred for two years. Then you'll have to run the thing for a few more years to get the *average* hourly cost back into a reasonable range.