The matter of the security deposit is known, it can be done via bank transfer, Bundesbank check, EC card, and cash payment is not possible. Since I have equity, that is not a problem. Of course, I only make an offer when I have a binding commitment. I have of course tried to reach a prior agreement, but I think that will not happen; the owners are divided and one party is even rather happy with the foreclosure sale. You won't be able to make a huge bargain at a foreclosure sale anymore, but rather get a somewhat realistic price... or be disappointed... anything is possible.
What would be so impossible about a sanitary installation now? Milling cable slots, laying pipes in advance, LAN cabling? And where it gets challenging, let the professional helper assist? There is nothing you cannot teach yourself.