If she has an agent showing the house, then she has the house listed and a comission is going to be paid.
Since a commission is going to be paid, go ahead and get yourself a buyer’s agent. As soon as the seller listed her house, you lost the commission amount as a negotiating chip.
You do your own research on costs. 2-3 written estimates for mold remediation would help with the negotiation. However no contractor can give you a firm price until they tear into the walls, and you really can’t be tearing out the drywall in a house you don’t own.
The mold should be tested. Most mold is just ordinary every day mold, and it can be cleaned up pretty easily. But if it is actually toxic back mold, I suggest that you walk away.
There are disclosure issues and liabiltiy issues. There are plenty of houses on the market for you to buy. You don’t need to purchase a problem house.
There are also plenty of house on the market for the home buyer to look at, and they are very unlikely to buy a problem house in this market. So your house would be hard to sell.
With ordinary mold, you disclose that it was tested, it was non-toxic, the source of the moisture was repaired, and the mold was removed. A few buyers will walk, but most can accept that.
If it was toxic mold, they are going to go and buy something else.
And no, real estate investors do not love mold. If the price is really good, it might be a purchase, but I would rather not, and I won’t if there is something else just as good to buy that doesn’t have mold.
If the house has mold, it has water issues of some sort. If the house has mold, it might be necessary to rip into all the walls. You are going to have a hard time determing how much replacement is going to have to be done.
Maybe you will be lucky and repairing a roof leak and wiping the walls with bleach might be all you need to do. But you might open a wall and discover it is in the studs and in all the insulation. There might be ground water issues, and occassionally, those are difficult to remedy.
If you are going to buy a mold house, the price had better be mighty good, and you had better have a really good idea of how extensive the problem is.