I’m no plumber, but one thing I look out for when I’m looking for a property is the state of the grass (if there is any grass). If it has moss growing amongst the grass, this is usually a good indication that there is some kind of a drainage problem. Could be due to run off from the rest of the property, or from someone elses. Hopefully not a leak from underground. There are many possibilities some worse than others, but its something to be aware of.