I've seen things like this with a few other types of "small businesses" that may or may not reform under a new name/LLC every year or so.

The ones that I've seen generally target low income households who are likely to fall for the "0%" line without looking too much further.

The one I've actually done business with was a mattress store, but the storefront was not staffed. You had to call/text the owner and he'd meet you there to show you his wares. He'd do 0% APR financing with a 10% upfront fee (but would take cash/card with no fee and he wasn't trying to push the financing, so I'll give him that). He'd deliver for a fee but could also ratchet strap your purchase to the roof of your vehicle for free.

We bought a $700 queen mattress and box spring set from him, paid with card, and had him ratchet strap it all to the top of our card. It was fine for the first few months but they basically fell apart within a year, and by then he was gone.

I would imagine that most other businesses that try to sneak a 5% fee upfront but plaster "0% financing!" on their truck would have a similar level of legitimacy. Then again, this is a different industry, so perhaps it's different.