what would OPPO do?

I purchased a house about 1.5 yrs ago. During the purchase discussions, I was told that the basement will get a couple inches of water in it once every 10 years or so. I have this written down in an email from the seller. That spring we had some crazy rain and the basement flooded. Ok so I should be good for another 10 years or so. Its flooded about half a dozen times since then and I am calling bullshit on what they told me. I wanted to finish the basement but would not want to do that if there is a good chance of water damage. Installing a french drain is a lot of work so will either cost me a lot of money or a lot of time. Would OPPO sue for the cost of the french drain installation or would you just suck it up and install it at a cost of your own time and the materials.