re: Any of you D.I.Yers ever build without a permit?

It could cause a problem. A general home inspection will likely not go looking for permits. I am pretty sure one addition on my current house was not permitted, not that uncommon. They have the option of buying with that knowledge.

When selling you have to disclose if additions/renovations were permitted. Most people lie and say they were, usually though they do not know one was needed for renovations they completed.

For instance, your A/C goes out on Friday night and the repair guy can replace it first thing Saturday. You need a permit. Gotta wait until Monday. (Or apppy for after the fact, and pay applicable fines)