I think the channel sounds awesome, and I would definitely subscribe. And I agree wholeheartedly about being very careful with the format. Sellers get weirded out by the idea of things in writing (captured in video), or their "personal info" being "out there". Also, I agree about production quality. I'm thinking that you should look closely at Wheeler Dealers. I think they get it right. The car-focused camera work and editing looks very polished when the cars are being sought initially, and at the end when they're being sold. The dialogue is good here too - they strike the right balance between on-camera vocals, and recorded voice-overs.
My real concern though is finding suitable candidates. Decent used cars often still have their big flaws - clunky suspension, bubbling paint, trouble starting, rattly interiors etc etc etc. A great $10k example of a "nice" Lexus on a reputable used lot can still need another $2500 to make it nice enough to truly be an example to the masses. If the idea is to make videos to show the true nature of this level of car...tatty details and all, then I suppose that's what you'll get. But, i think examples of cars that are really editorial caliber may be a challenge to come by on a regular basis. Id think that getting chummy with a used lot manager who really moves a lot of steel is going to be a good bet. Or, get close to a car detailing pro - they may have clients who would be proud to display their collections.
This is just food for thought, not trying to turn you away. Like I said, I think the concept sounds quite entertaining, Id watch for sure. If you're able to make a successful go at it, I bet it would be a ton of fun to do!