Uhaul usually only rents their vans (be it moving or cargo), they don't offer them for sale. Budget Rental Car and Hertz does offer their vans for sale after they've hit a certain mileage.
A used cargo van can be bought at Used Trucks, Uhaul, Commercial Truck Trader, Enterprise Trucks and Cargo Van Go. A large number of cargo, utility and delivery trucks are available on those sites so you could browse and select the best for your requirements.
UHaul, Value Cargo Vans and eBay Motors all sell cheap used cargo vans. Local car auctions can also be worthwhile as they often include impounded vehicles which are sold off cheaply to offset parking or traffic violations.
I would think of uhaul as place where I can get these used international trucks. It just makes sense for me to at least try there when it comes to this item.
If you are looking for stores that have used cargo trailers for sale, take a look at Tucker's Trailers and RVs. They have a good and decent selection of cargo trailers that you can buy.
I would check out ebay motors and buycargovan.com. You might also be able to buy a good used one from rental car places like budgetcars.com and cargovan.com
Cargo vans can be used for whatever you need them to be used for. If you want to use one for your maintenance company, that sounds like a good idea to me. You can probably find a cheap one on craigslist.
All U Haul trailers are built by U Haul I you want one you will have to buy it used from U Haul They have a very good website
Cargo straps are used for ensuring that cargo is delivered in one piece. Many cargo units have smaller items inside and the strap prevents them from leaving the main cargo.
One of the best places to find used cargo trailers is on eBay, as there is a wide range of different products available. One would have to find a product that isn't too far away from them, but due to the massive amounts of cargo trailers being sold, that would not be very hard. One can also buy used cargo trailers from their local trailer store, which can be found in the Yellow Pages.
That would be a cargo rack.
You can buy cargo trailers from dealerships, ranch warehouses, and specialty stores. You can try WSS Trailers, Colony Cargo, and Trailer Shopper. Used Vending sells used cargo trailers.
There are lots of places where you are able to find a used cargo van, one of the best places to start would be Kijiji. You can also find used car lots listed in the local paper.