I have a castle for sale for 4500 BTC, or serious offer 
Where at and will you owner finance?
We are talking about the famous Bitcoin Castle in Malla, Estonia. And no, you don't buy castles on credit
I have a better idea:
Apply for financing to finish it, make it a profitable business and then sell it in shares.
You might want to organize a share issuence for instance via invesdor.com for finishing the building.
After that sell your share to someone else, but before that it obviously need to make profit. Nobody wants to buy a business that loses money.