I'm not saying owning a Cummins is a bad idea, but don't buy one for fuel mileage, to save money, or to use as a daily driver: you will be disappointed, pay a small fortune, and eventually run into big-dollar repair bills. Diesel mechanics is an art of its' own and most of us can't do it ourselves.
I love diesels, and I love my diesels. I've had 6 over the years. I had the first 89 in this zone, an 06, two Duramaxes (or is it Durami?)(meh) and a TDI VW, but my '92 is awesome. Yeah it's loud, smelly, dirty, rough riding and it smokes but I wouldn't want it any other way. And yes I do all my own work.