I am new to InDesign and we have a contract employee that builds and creates most of our ads for us. When we lay them out on the page, the ads look fine, but when we get the newspaper back from the printer, the wording in the ads are very blurry and some are almost illegible. Our printer prints in CMYK and I have been told that this may have something to do with it. Any suggestions on why this is happening and what can be done to fix it? (By the way, this happens on both color ads and b&W ads)
The color space of the artwork wouldn't affect the clarity, only the vibrancy and appearance of colors. This sounds more to me like your ads are not created at a high enough resolution. If your ads are mostly text-based, you may want to see if your designer can provide you with vector versions of the ads. If not, ask for 300 dpi CMYK images, typically in TIF format.
Computer monitors have a display resolution of 72 dpi, whereas the printing standard is 300.
This could explain why a lower resolution design would look fine on your computer but appear blurry when printed. Printing these ads would be in essence blowing up your design to fit the print medium. If you've ever zoomed in on an image and seen how it gets blurry or pixelated on your screen, it's kind of like that.
Your problem is most likely your output to the printer fails to provide the fonts. Your printer is simply rasterizing the font from the preview image stored. I would guess you aren't providing a PDF? PDFs solve this problem fairly well by allowing you to embed the font information. The other way around this is to convert your fonts to curves (vectors) if you are using Corel, Illustrator, or some Drawing application. If you are using InDesign, Quark, FrameMaker I would suggest you do things the standard way. Don't let your printer tell you how to do it. Tell them! You should know the issues. (Rule #1 of Graphic to Press)