I much highly suggest to use OTC to buy, much safe, especially the buyer don't have any idea.
Definitely, yes.
When such large sums of money are involved, I would always fall back on an institution with which OTC trading is conducted. In my opinion there are 2 options that come into question:
- Exchanges like Bitfinex, Bitstamp and Kraken which offer OTC-tradings
- Institutional OTC-brokers ... but I honestly don't know if there are brokers who offer bitcoin trading, too.