Everyone else has pretty much covered the Military conversion angle. Don't.
Trucking can be a very hard life, and owning your own truck is about twice as hard. I take it you are not currently a truck driver (judging by your questions) so, my advice is, drive someone else's truck for a few years, then maybe think about owning your own. As for leasing a truck (which is not likely to happen without a few hundred thousand miles under your belt), I equate most leases with indentured servitude.
There is a lot more to owning a truck than just driving it. Last I knew, it was about $120 just for an oil change. That is just for a start and the costs only go up from there. If you do most of your own maintenance, you spend most of your "free" time doing maintenance. Any truck you buy or lease is going to break, and it will be expensive. Even if you buy a brand new truck with a warranty, down time is expensive. Wheels that are turnin', are wheels that are earnin'.
You do not own the truck, it owns you.