If proofs of payment are provided but in cryptocurrency, do you think the court will consider it even though transactions are tagged illegal with it?
Please don't make the mistake of basing such a crucial decision on an internet forum, especially from advice given by total strangers. Consult a qualified lawyer instead. If Bitcoin is illegal in your country, avoid using it for any purchases. Even in countries where Bitcoin is legal, buying property with it doesn't make much sense. The reason is the taxman. You'll likely be creating a complicated situation with tax authorities by purchasing property with a non-legal tender.