Yes, husband and wife teams are the only ones I have personally spoken with that we able to stay a team for longer than 6 - 12 months.
Money maker?
Well, if it has a custom manufactured sleeper with all the goodies installed...it could not even legally load 2000lbs of cargo.
Think not? Go back and read the post of the guy who bought two of these vans, loaded up their personal items, fueled the vans, drove them across the scale, got a weight ticket and showed up for orientation.
The carrier had a minimum 2000lb cargo requirement and the vans were not even close to meeting that requirement. Needless to say, they were turned away by the carrier.
He drove his $90,000 investment (both vans) to a nearby dealer that sells a lot of these vans, took a huge loss and sold the vans. I saw them both parked at the dealer.
Therefore, two aspects come to mind:
First, with that set up...how many are operating illegally?
Second, with that set up...how many are exceeding the manufacturer's engineering parameters?
Considering the high incidence of transmission failures... question two has already been answered and by default, that also answers question one.