Must be nice to have that kind of money for such occasional use! As others mentioned, consider a used truck. I personally like my DEF Ram, they get better fuel economy and require less maintenance since the engine runs cleaner. I found a used 2015 and saved a couple thousand bucks. I've had the truck for a year and a half and there isn't a single problem with it!
To answer your question, it should be fine. Research and buy an appropriate diesel fuel additive. You don't want summer blend fuel freezing and gelling in the winter. You don't want to worry about algae growth, etc.
If you buy a DEF truck, keep an eye on your DEF levels. DEF has a shelf life that is shortened by heat. Don't keep your DEF levels full if you plan on leaving it sitting. Buy smaller packages (maybe 1 gallon size) and only use them when you plan on driving. If you fill up your tanks and park the truck for 9 months in the summer, you may have DEF problems.
Keep an eye on the batteries to ensure they don't lose charge. A quality trickle charger is your friend here.
When you do use your truck... USE IT. Don't drive it like a little old lady, they like to be worked, they like higher exhaust temps to clean out the DPF. If it were my truck, I would try to drive it a little more often though. Every month or so I would try to take the truck out for a longer highway drive. Get the fluids moving and up to temp, the exhaust up to temp, splash some oil around inside the engine.
If you are going to use it to pull a heavy camper, look at a 3500 instead. The 2500 is class limited to 10K lbs GVWR, which leaves about 2500 lbs payload with the diesel. The 3500 has a higher GVWR, so a higher payload rating.
