What Bob Crane and Barbara Todaro  said.

Are you an agent, a buyer or what?  How were you nearly ruined?  Permits don't necessarily solve problems like this, nor do licensed contractors.

But chances are that the issue can be solved without financial ruin if you have competent contractors it may just be a simple fix.

It starts at the beginning of every conversation you have about real estate and never ends.

Responsibility begins when obtaining a license.  

If you were working with the listing agent than she owes you pretty much nothing, IF she was a dual agent she should have at least disclosed the illegal addition.  If however, this agent claimed to be your buyers agent than she is responsible.  Her fault. 

Most contracts stipulate that any repairs needed to be done before closing need to be by a professional... but you also state that the home inspections found nothing, so that part is confusing.  I have never had a home inspection (even on brand new) where the inspector came up with nothing. Who picked the inspector? 

A good buyers agent checks for permitting and also a good inspector picks that up illegal additions in their inspection.  You can always tell by just looking.

Unfortunately  you were not represented,  No need to temper your words...she did a crappy job.

Eve

An agent's responsibility begins with the agency agreement and legally it ends with the closing -- although of course lilability extends farther.  In NC agents are held responsible to disclose unpermitted space, so the listing agent has an obligation to disclose it, and the buyers agent has an obligation to investigate the status of any additions.  That said, some additions/improvements are going to slip past because there's no obvious indication they were  done after initial construction.  

It begins when you get a license and never ends. Your estate may be held responsible for the damages you caused even after you die.

Michael Jacobs nailed this one...

Jackson Stieb - the responsibility may start on the day you sign them as your clients - however, it continues as 'relationship for life'!

Why should it end? May be from legal perspective, I guess...

The agent is there to represent you and help negotiate. An agent cannot do the home inspector's job, attorney;s job, termite guys job, surveyor, lender, etc. Those people are responsible for their parts of the transaction.

Hope they are clients for life.

As a fellow Californian I can tell you that a permit check would not have helped them any.  A permit doesn't look to see what size nails you've used.  They check things to sign off on the construction (assuming they ever come out), but they look for the major stuff (from what I've seen).  In my city of Thousand Oaks a records search is a required part of the transaction, but it still won't tell you if the nails were too long or who did the work... or if the work was even done!  I had a house listed that had permits pulled for a garage conversion and a pool... but it had neither.

I don't recommend permit searches unless there is a discrepancy between what the assessor and appraiser says or if the client is concerned.

I would think that your inspector would have pointed out all of these issues to you with the inspection report.

     If "nothing came back from the home inspection", and then you found this problem, you should contact the inspector and ask what they intend to do about it.  

     If the Inspector (who missed a glaring defect) says "nothing", then see an Attorney.

This is the kind of thing that a home inspection usually red flags.  If your agent talked you out of getting an inspection, it's one thing.  And if permit checks are the norm in your area, same thing (they are not here). I'd ask, where does the buyer's responsibility begin and end?

it's the job of the buyer's agent to do that....but as listing agents, we also do it to make sure the seller has done everything correctly....if there is a permit outstanding, we have a final inspection and a signed off permit....if none were pulled, we have the seller walk into the building dept. with his head hanging and pull a permit.... take the penalty and get it done right...

so, to answer your question, the responsibility starts at the beginning and does not end until closing....

With you as the agent

When you get a license and never ends.....24/7

I would have to say everything in the middle of those starting and ending points.

24/7 if you want to be successful.

An escrow refused to close because the roofer put-in longer nails than needed and they protruded out by a 1/4 of an inch all around the eaves of the home. Rust could develop, rot potential and aesthetics all came into view & consideration. We had to hire a man, to go around and snap off that 1/4 inch before we could close. In this case, the remedy was a money driven solution not an argument. Point: Agents must solve all problems no matter what or what is the point of licensed help?.

Licensed day, still working on the end

The others have answered.

It starts with an Employment Contract

Not clear whether you are representing buyer or seller here, so any comment as to your role in the transaction is hard to make.