What is the risk of an Inactive/Expired CPA doing my taxes?

As long has he is not holding himself out as a CPA, this is no big deal. Most morons at H&R Blockheads are not, and never were, CPAs. A CPA license is not needed to do taxes. A red flag however is if their license was revoked. THEN you would want to ask questions.

Ask him why. I wouldn't have a problem with it as long as he wasn't suspended for doing something wrong.

Unless your taxes as very complex, the expired CPA should be ok, or many preparers that don't have a CPA.

It depends on where you are. In my state, California, you have to be in good standing as an attorney, CPA, Enrolled Agent (like me) or enrolled with the California Tax Education Council before you can prepare tax returns for pay. Most states don't require you to have any expertise before you do tax returns. If the person you have encountered has just let his license expire because he has retired or does want to practice actively AND has a preparer filing number there is no problem with using him if you trust his ability to do the job.

You don't need a CPA to prepare your taxes. That being said, you can ask if they have Errors and Omissions insurance, in the event they screw something up.

they don't take the classes because that costs money.. so yes there is a risk if you use them because they may not be up to date on all the tax law changes

In order to do taxes, he has to have what's called a PTIN. CPA's are exempt from the continuing education requirement, but if he is not maintaining his CPA license, he would have to take at least 15 hours of tax update courses per year. If he is semi-retired, he may feel that the expense of maintaining his CPA license isn't worth it.