Yeah, my main concern is which will be lower total cost and have the best warranty coverage?

Here is a more specific example;

A family member is looking for a 2007 3-series. So if they by used from a private seller, it will have 3 years or up to 50k miles on the original warranty. Then they will have the option to extend the warranty, which can be another 2 years or 50k, right?

From what I understand, the CPO warranty (2 years or 50k) kicks in after the original manufacturers warranty of 4 years or 50k miles expires, but from what I have read, it is not as comprehensive as the original marufacturers warranty or a typical extended warranty.

It seems like you would be better off buying from a private seller (no sales tax and typically lower price) and then buy an extended warranty yourself after 4 years or 50k miles, instead of paying the tax and dealer markup to CPO the car.

Does that sound about right, or am I missing something?