What would you do if armed men arrived at your house, demanding money under threat of kidnapping you, or the threat of simply stealing the amount of money they would like?
Government has the monopoly on force... there's nothing you can do if they come and demand explainations as to where the money that you used to buy the real state came from. What would you do?
When you want to purchase a home, you need to pay the welcome tax, the notary and all the feed that come with it. The best should simply convert the bitcoins you have into fiat and pay the tax associated with that income. Then pay a cash down into your house and borrow the rest with your bank.
If you are rich, you could buy it cash with your bitcoins

Like I said before im not rich, and even if I was rich, it would be impossible to get not even $100k in cash, nobody in Localbitcoins is going to meet for such a big amount, it's just crazy, and a penthouse is usually half a million, it's just not going to happen. There's no way out other than converting your bitcoins to fiat and paying taxes.
put the deed in the name of a trust.
make sure you are not the beneficiary of the trust. but another trust is the beneficiary.
you then set yourself up as just an administrator of both trusts and take a fee for services rendered from the trust.
oh and make sure the bank accounts are set up under a foundation too. that way the fiat can flow without it evaporating. and because the funds dont legally belong to you no one will knock at your door
its how the fat cats get away with not paying tax.
To be honest I have no idea how any of that works. How are you going to open a foundation out of nowhere? and you mean a trust fund? I wish I could understand all that economy jargon... honestly I would be scared to do that, im sure they can end up finding out you are fucking with them.