More often than not. 

Paul S. Henderson, Realtor, Tacoma Washington I came across it once with a deck. The owner's may save money in the short term, but not in the long term.

Some things practically scream out to me --- literally and figuratively.

It happens.  Though, there are times it's difficult to tell.  I do advise the sellers that it will most likely become an issue during an inspection.  

All the time. I can always tell and will ask them about permits on the spot.

Thats what home inspectors are for.

Permits are not required everywhere and for everything.  The important question to ask is, was it done right?

Paul - Many of the investment properties (as well as older remodeled homes) have had projects that you could tell were do-it-yourself projects, and you know there were no permits issued. There are more of these than I wish there were that's for sure.

Often, and some are at least equal to professional work so it's rarely been a problem except for work that requires a permit. In those cases I always get a licensed professional to inspect and do the paperwork for a permit prior to listing the property.

Every week at least 1, it is not that uncommon. It is the ones done wrong that stand out though

Do it yourself projects are very common. This is another good reason to opt for a professional home inspection.

Not too often due to the caliber of homes we market.