Not a beginner, Capital isn't a problem, I run a crypto based business and am always looking for sources to buy large amounts of coin at good rates.
I'd say probably Localbitcoins[1], as you wouldn't have problems with banks and taxes and stuff because you can purchase peer to peer, even with physical cash. Though I'm not sure if you can call it "good rates" though. I suggest posting your own offer for optimal rates.
[1]
https://localbitcoins.com/Localbitcoins price usualy depends on the current mood of the traders in your location. In my city you can always buy crypto for +15-20% over the coinmarketcap price and sell for -10%. OP might try to pick some safe and popular payment methods get some trades on localbitcoins for better trust and then place his buying ad. As I remember he will need about 0.1-0.2 BTC to make this ad visable on the website but a chance to buy crypto below the market price might worth it.
Purchases with higher benefits are usually connected with higher risks (like buying / selling via Paypal etc.).
Why even go through the stress of a peer to peer transaction. I do not see $10000 to be a huge amount. All he needs is to get verified to the highest level on most of these exchanges and he will be able to buy directly from those exchanges. For example, I make use of Luno around here and I can make transactions of more than $10000 in a month without any issue. I even feel P2P methods using localbitcoins come with much risk and the rates sometimes can be pretty high.
For large amounts like that, just as someone already mentioned, localbitcoin is your best bet. More like a peer to peer transaction without the involvement of a third party. Most especially for such an amount. Also, if remitano is available to you, you can try them out, as their platform even includes escrowing of funds before releasing it once all transactions have been confirmed.
