Once you start mining, you will get a steady stream of income. In any case, if you want to cash out to cover costs that you cannot pay in bitcoin, you will most likely have to trade your coins in an exchange. Under no circumstance should you leave your coins sitting in an exchange. A number of exchange have been hacked or have outright stolen customer funds. Be smart. Here is a list of exchange that are quite popular.
- Poloniex. Large volumes, trade major crypto currencies.
- Bittrex. This site has been online for a long time and has a wide selection of crypto to trade.
- Kraken. Large established exchange.
- C-Cex and Yobit are smaller exchanges, and feature smaller altcoins.
Some exchanges permit you to lend out your coins to other for a fee. This means that on the flip side you can sell short those altcoins, by borrowing the crypto at a fixed rate. Some also offer margin trading (on borrowed funds).