Estimating jobs...

Man I cant seem to get a handle on estimating jobs.

I always end up working for free.

With wood working I know how long a job should take beacuse I've done it but with these old cars and especially on fancy show cars, I have no idea how long it will or should take.

Where I get screwed is I cant afford to turn away work so I bid it on the low end. Then as we all know a million little things happen and now I'm working for free.

I would love to just bid by the hour but even then it can go bad as the customer has no idea how hard it is to wire an entire car/truck in a fashion that fits the build.

My problem is I want everything perfect and I cant stop and say well that's all they paied for...

With wood work I got to make all my mistakes on my boss dime now it's all on me and the stress is almost to much.

I feal like I'm so close to loosing it all but at the same time I'm doing cars and have customers that are so far out side my comfort zone. If I can just pull it all off this crazy idea could just pay for it self or even, God forbid make me money....

How do folks do it?