Well, Steve.... I would never want you as a customer, as it sounds like you'd never be happy with my work.
Having said that: I take a one hour minimum diagnostic. Period. I pre-qualify all my customers on the phone, and even talked some out of fixing their unit, as it was just not worth it for either of us.
If I don't work on something, like for example Nakamichi Decks, I refer the customer to someone who DOES. I don't stock NAK parts and feel a specialist is better for those jobs.
Then an estimate. Which is exactly that. An ESTIMATE.
If work is approved and performed and I am successful, I expect to be paid.
If I fail, I do not charge for the "work", but my 1 hour minimum stands. I very, very rarely fail. Yes, I am good at what I do, but sometimes things don't work out due to some part no longer available. Anywhere.
SOME jobs get out of hand, but in my case I love restoring reel to reel decks, so at some point I just flat rate the job. I want to fix the machine and the customer to be happy AND come back with other work.
I NEVER advertise. I work from home. So my reputation on the internet was truly earned and I am grateful to have it. It's ALL word of mouth, so there is ZERO incentive for me to cheat anyone. In fact, I don't need to do this at ALL, so you can go piss up a rope for all I care.... I do this because I like it, and in the end it pays for the food... which sure is expensive these days.
In the end, if you don't like it, learn to do it yourself. We are all retiring soon and you can complain to someone else. 2 years for me.