wherever you're buying them from, DO NOT leave them in an online exchange.
Here's what to do. Pick the exchange you want to use, set up with them and do $5000. Pull it out, put it somewhere ELSE - Armory, etc. Verify your money with a private key known only to you is in the blockchain. Then do another $5000. Rinse, repeat. Up it to $10000. Pretty soon you are done.
That is almost exactly what you have to do, but may be in little portions. Risk less and be safe

Withdraw at the moment you have the deal.
Best Regards,
Gondel