It's not clear from your post if you are thinking of this to flip and sell, or thinking of this as a way to get a home for yourself to live in at a good price.
If the former, take into account that you'll probably have to disclose the mold fix to buyers, and buyers will probably not be interested unless the fix is sure. Basically, if you are doing this to sell, you are going to have to do this the right and careful way.
On the other hand, if you are buying the home for yourself to live in, you don't have to be as careful. You might be willing to go for a cheaper solution that has, say, an 80% chance of taking care of the problem, taking the risk that you'll have to do more later, whereas a buyer is not likely to find that acceptable.
In other words, people have different levels of risk they find acceptable. If the house is for you, you only have to bring it up to your level. If it is to sell, you'll probably have to bring it to a higher level.