Anyone interested in buying bitcoins needs to deposit funds in U.S. dollars, euros, or another currency supported by the exchange. The popular methods of transferring money to the currency exchanges are through bank wire transfers, credit cards, or liberty reserves. One of the pre-requisites here is to have a digital wallet to hold bitcoins. Bitcoins bought can be stored in a digital wallet, device, or paper wallet, depending on the buyer’s preference. For sellers, the fait currency for which the Bitcoins have been sold needs to be withdrawn from the exchange and sent to a bank. One issue that can arise is if the exchange has liquidity concerns at a particular point in time; such situations can delay withdrawal and transfer of funds into a bank account. (For more, see: A Look At The Most Popular Bitcoin Exchanges.)
Making money arbitraging bitcoin futures can be extremely simple. Futures contracts typically trade at a premium, and all you have to do, starting with USD, is buy bitcoin at Spot price and sell futures of the same amount at premium price. Then just wait until expiration to make your arb profit in bitcoin (which you can then put in USD). Whether it's a weekly, monthly, quarterly, or any futures contract, as long as it's in a premium, you lock in the sale price and earn the arbitrage profit.