We had a "certified environmental tester" come to our Eichler to test for mold. Based on some lab results, he might make recommendations which might include drilling into walls, ripping out toilets, fun things like that...
Before we go that route, I'd like to make sure this guy is for real. I checked the CSLB web site, and it seems that there is no license category for "environmental tester" or "mold tester". Should this person have a license? If so, what license category would it be under? If there is no license for this category, is there another way to make sure that you're getting someone trustworthy?
I don't want to start a flame war, but here goes. "Toxic mold" is mostly a home repair scam that's grown up in the dry southwestern states starting in Texas and spreading westward. It's been pushed along by some unethical doctors too. Fungi (mold, yeast, mildew, whatever you want to call it) are extremely allergenic -- so are cats, but that's about it. Nobody puts on a hazmat suit to come and take Fluffy to the pound and you don't need to get any more panicky than that about mildew -- you just need to get rid of it. However, if you have a leaky roof or leaky plumbing or poor ventilation causing mildew, then you certainly need to get it fixed, because houses are made of wood and wood and moisture don't mix too well (unless you're a termite). If you see visible mildew, wipe it down with bleach, and find out where the moisture is coming from that is giving it a chance to grow. If you can't see it, it can't hurt you.
If you have been diagnosed as having a medical problem due to toxic mold, I recommend that you see a reputable allergist. I can probably guess the name of the doc who diagnosed you, too, and I live in southern CA!
If you are worried about mildew under the toilet, go to HD, buy a new wax ring, drain the potty, undo the two bolts at the base and pull 'er up. Do not pay someone for such a simple task. Yikes! I just put in two new ones this weekend. It didn't take but 15 minutes each, mostly spent looking for the wrench.
Oh yeah, I forgot about food borne molds like aflatoxins. They are potentially carcinogenic, so avoid moldy food.
The shower stalls in Eichler bathrooms can become mold laboratories if not properly ventilated. The installation of a fan is the best thing you can do to avoid this problem.
Did the "environmental investigator" have suggestions for you on mold prevention?