How would you transfer the btc to your bank account without making the Banks / OECD / ask questions?
And even if you get cash from localbitcoins someday the efforoties may ask you from where this car or how you bought this house..
What would you do ?
First of all I wouldn't sell all 500 Bitcoin unless the price is extremely high ($1000). I would sell some and store my rest somewhere safe. If you do sell 500BTC, then I would just say the exact reason to the efforoties and to the bank. After all, it isn't as if holding Bitcoin is illegal in most countries.