A truck can be flat towed, but the short wheel base of the toter would not be safe in my opinion. In my past I ran a heavy duty wrecker, and have towed trucks of all sizes, and have flat towed a few with a smaller truck when our large wrecker was out of service. The towed vehicle tends to want to go straight due to the caster angle of the steering, when cornering its going to try to resist and the back end of the towing vehicle can be dragged sideways, ending up in loss of control and a jackknife. The tow bar does not transfer any weight to the towing vehicle, and if you do not have enough weight over the tires, your ability to stop or pull a hill is greatly reduced, remember there will be no brakes on the towed vehicle to assist with stopping. This will further increase the possibility of a jackknife. Backing up a vehicle on a tow bar is bad news also.
Check with your local laws, I think you will find that most areas will have a requirement for operational brakes (and usually an emergency break away switch) on any vehicle over 1,500 pounds or so being towed. (there may be exemptions for vehicles on a tow truck) Some areas also do not allow flat towing of vehicles over a certain size. for towing junk vehicles you may need a transport plate, which will usually only cover vehicles on a conventional tow truck.
More than likely you will be in a weight class requiring a class A CDL license. As you are doing commerce there may be all types of permits, paperwork and the like.
The only safe way to do this is with a tow truck properly set up with a sling or underlift that will transfer the weight properly to the axles.
If you look around you should be able to find a reasonable price on an older large wrecker or at least a body that you can have installed on used truck. Some of the old Holmes 750 split boom units are still hanging around. Might also find a used Zacklift hydraulic underlift that can be installed on any used tractor.
Make sure you do your homework on the local laws where you are, and make sure you do not find yourself getting stopped and fined by the Police & DOT. and you defiantly want to be covered legally and by insurance if an accident should ever happen.