If you choose to splash out on a castle then be sure to do a lot of investigating beforehand - very often the ownership rights are unsettled and you may end up buying something someone is going to want to reclaim (as rightfully theirs) in a couple of years... Lots of nice places in southern Poland, BTW.
Indeed. There are a few large houses (palaces even) in Poland that are virtually unsaleable. Sometimes because of ownership issues, but mostly because of the cost of renovating historic buildings. One of the Warsaw real estate magazines, a couple of years ago, was advertising some amazing houses, even for as low as $5000, but the downside is that they were uninhabitable, often with half a roof, and could only be restored by architectural specialists and art restorers who are not cheap.