If I was buying a used tow vehicle and didn't have the background to inspect the vehicle thoroughly (I do), I'd pay for an inspection. Multiple owners may indicate a fault in some part of the vehicle. Or, in today's mixed up financing world, it may be only a monetary thing.
One suggestion I'd make when choosing a tow platform is to forget about fuel costs. If you used a calculator and accurately estimated fuel costs from the highest possible to the lowest, you'd find that the difference in costs is meaningless. There are some that will disagree with that outlook, wishing to keep costs low while not towing and gaining that benefit. In most cases that will be less than $1K/yr. and that may absorbed by reduced repair and maintenance by the heavier cost vehicle.
FWIW, one year I spent over $11K on fuel for road vehicles. I do know about fuel costs.
