I'm an accomplished A&P and a current IA. I don't charge commission — I charge a flat fee, with no additional fees. I'll look at as many planes as you want. It doesn't matter how long it takes; as long as you cover my travel costs, I'll go where you want and check out what you want.
The reason I work this way is simple: it means I don't have a dog in the fight. I can give you my honest opinion and tell you exactly what I think about a specific airplane.