Cheap way to test for mold spores

“Water quality” is not one-dimensional … what kind of contaminats do you want to test for?

If the answer is “everything” or “I don't know” then start by finding a reputable local lab, describe your concerns to them, and see what they recommend based on their knowledge of the water in the area. Once you have done a thorough one-time test, you will have a basis for deciding what (if anything) to test for on an ongoing basis.

To find a lab, you could start by calling the water authorities in your town or surrounding towns. At least in my case, they were happy to recommend a local, independent lab.

If you've had problems with water damage in your basement before, there is a really good chance that you have mold. The downside is, it can be hard to detect mold on your own since it can grown within the walls or under carpet. You can buy a mold test kit from somewhere like Home Depot to check on your own. I would probably start there if I were you and if you see you have a problem, then I would probably call a professional. Especially if you've noticed a decrease in air quality in your basement.