Buying county foreclosure sale - title search?

You better do it. There could be a nasty surprise or two waiting for you. If you are going to buy, you will want title insurance and as you said the lender will require it so ask a title insurer what it will cost. It shouldn't be terribly expensive and there is what is known as a preliminary report which is much cheaper but doesn't dig as deep. You may wish to get one of them. Good luck!