Looking to start a cash by mail service on LocalMonero. Tax advice?

I'm looking to start a a cash for monero business on LocalMonero. I will being posting a "sell to me" type of ad as well as a buyers ad. Obviously I will be withdrawing/deposting large amounts of cash to send to customers as well as buy more monero from an exchange. Does anyone know how to report gains on your taxes without the IRS trying to tax the whole amount of cash? Do I just report the profit and hope for the best? Does anyone have experience with any crypto friendly banks or brokerage accounts?