Trading BTC from Hardware Wallet Costs?

This is a follow up to my previous question. If you want to buy BTC and transfer security deposit from a Hardware wallet, is it necessary to do two bitcoin transactions, and pay two mining fees?

  1. Transfer BTC from Hardware Wallet to Transaction address and pay mining fee for this
  2. Purchase or sale of BTC (the actual transaction) and pay mining fee for that? Does only the seller of BTC pay the mining fee for this part of the transaction?

Please let me know. Thanks!