@Mark Gruetzmacher,
In spite of what @Marc Faulkner has said, mixing bleach with water only kills some of the mold. And it is IMPORTANT to note that even if it (or some other product) did kill 100% of the millions and millions of mold spores, hyphal matter, bacteria, etc., the presence of a dead mold spore is just as allergenic as a live mold spore. Killing mold - especially when you've had as much as you described here - will not solve the problem
Hidden Molds
Even if you were to take the shortcut - and take your chances (legally speaking) by spraying something on the walls to kill the obvious molds, you can't spray into the area behind the wallboard. Mold likes to grow in dark and wet spaces. Mold even likes to grow in that space where the wallboard meets the wood. The process of killing mold only on the areas you see - in your particular instance - will have no effect on the molds on the backside of the wallboard, on the hidden structural wood, or inside of the insulation.
I might even go so far as to say that you should consider removing the belly board materials - which are usually OSB or ChipBoard (also known as WasWood - it was wood once, but not any more). These are only one level up (on the structural ladder) from gypsum wallboard. This means that these surfaces can also grow mold very easily. There could be some on the top side of the belly board in areas where you can't see it. i would recommend that you check that space very well before you make any decision to keep or discard the belly board.
Structural Integrity
I have little doubt that having that much water saturating wallboard, structural wood, and insulation for any time beyond a week will seriously compromise the structural integrity on 2 of those 3 items. Structural wood can get wet and dry ... get wet and dry ... and get wet and dry many times over ... but first, you have to dry it in a timely manner. That was not done here. Consequently, saturated wood that does not have a chance to dry turns into mush. There are all kinds of scientific (i.e. physics) reasons why this occurs. Suffice to say, wallboard, structural studs, insulation, etc. that has been wet that long needs to be discarded.
Killing Mold versus Removing ItThere are many products and processes to kill mold in place. Very few - and I do mean VERY FEW are effective. Here is my point:
While it's true that some folks react to the mycotoxins created by live molds, most of the asthmatic and allergy-prone individuals who react to the presence of mold are reacting to the proteins in the mold body.
Picture a mold spore being in the shape of a football or even a soccer ball. Now let's say you're killing it in place. You don't destroy the shape when you spray or otherwise treat the surface. That "shape" of the spore is made up of millions of protein particles created as the mold spore grows and develops. Killing it doesn't make (DOES NOT MAKE) the shape go away. Consequently, killing it does not make the proteins go away.
As I said earlier, most people who react to mold, react to the proteins. That means that killing a mold - as opposed to removing - leaves it there for the next allergic person (your tenant maybe?) to react to it.
If you want the mold problem to go away, don't bother killing it. Concern yourself with getting rid of it (through removal / remediation). There are no if's, and's, or but's about it! Removing the damaged materials is the only way to be sure that the mold you find won't be a problem in the future.
Your Eventual Liability
First, +1 on what @John Arendsen just said!
You don't normally ask your tenants the extent of their allergies or asthma. Heck! If you did, one of them might come after you with a lawsuit using The Americans With Disabilities Act. Rather, you assume that they are in good health unless they tell you otherwise. (I am not an expert on what information you can ask potential renters, so you'll have to visit another forum here on BP for better guidance on that point.)
If at sometime in the future however, one of your tenants does react to the air quality (because you missed some molds or did an improper job of cleaning it up) then you will be party to a lawsuit.
On the other hand, if you address it correctly, and hire a professional company to do the remediation, you rely on THEIR insurance to confirm that the work was done correctly and in a professional manner. Financially, the difference could be a few hundred vs. a couple of thousand - today - but could certainly be much, much more if you get sued in the future.
Finally
Although I am not an expert on what you can ask the potential renters, I am an expert on mold. I have been involved in countless mold contamination projects ranging from mobile homes, to light commercial, to large and high-rise commercial, to educational environments (elementary through college level) since the early 90's. And because of that I say that you should use a professional any time that you want to address mold correctly, using the latest standards, engineering controls (to prevent cross-contamination), trained staff, be covered by THEIR insurance, etc.
I realize that many people here on BP have chosen to do it themselves and some of them don't ever have downstream problems. Not everybody has that kind of luck though, and if you have a renter with sick children who suddenly can't live in a home you leased, then they will come after you.
Please post any follow-up questions or comments here and I will certainly try to respond to them.
Travis West
CIEC (Council Certified Indoor Environmental Consultant)
MAC0325 (Mold Assessment Consultant; licensed by the Texas Department of State Health Services)