My opinion is there are too many uncontrolled variables. The only way you can safely overcome the variability is to plan very well. Some risks to consider:
Vehicle's actual condition. Those Ritchie brothers have a different motivation than yours; so the condition they report the vehicle to be in is already slanted. Add that there is only so much they can do to sniff out latent discrepancies even if they were motivated to report accurately. So how do you set your bid limit if you have, at best, a poor idea of what it needs to become a $20K truck? The risk to us regular folk is up to us, we accept the risk because it's one vehicle and it won't ruin us if we bid $XX and the delivered cost is $15K, and oops it needs another $15K to be roadworthy; press on or cut your losses.
Vehicle availability. The trucks you'll want/need to bid on, (good running condition, most of the parts still there) often exceed your low-limit selling price after you factor in fees, tax, and delivery. You'll be competing against the regular folks who are willing to drop $15K for a truck they estimate they can get roadworthy using their own free labor.
Parts availability. Some parts are easy to find at some times, some are hard to find some times, and others are hard to find at all times, but there's no way to plan this aspect. For example, if you buy a truck that needs a radiator, and as circumstance would happen, no radiators are available, then what? How long can your business and workers sit idle?
Customers. Are there enough actual committed customers to justify the expenses? There are several companies already in business doing more or less the same thing, and they've already worked out the details. What would you be bringing to the table that's different? WE buy them because we like them, all the idiosyncrasies of military vehicles notwithstanding. For example, I don't care that the ride is rough, it's satanically noisy, there's a milsurp smell about, or that it's drafty. I wouldn't pay $30K for it though. So your only option would be to convert them to Hummers, which would blow your budget. The mil-vehicle market is already schizophrenic; some people turn H1s into military looking, others turn HMMWVs into H1s, and still others take either one and customize it to some specific need.
Johnny Law. There's 50 states and 50 different sets of law on the books, ranging from fuggetaboutit to sure-whatevah. Within those sets of laws are interpretation variables; it's supposed to be legal but Sally Licenseplates doesn't let it through. Beyond that are many many other legal implications- like liability (thing's a deathtrap) and training (nobody told me I couldn't jump it).
These are just some factors off the top of my head that would be very hard to plan for. You'll also need personnel that know these trucks to be efficient.
If you want to do this, I suggest you get in slowly. Start with one truck, go through the (sometimes miserable) process of bidding, getting it to the shop, and then see what it takes to turn it.
