When Bitcoin just started many years ago, it was still possible to mine Bitcoin using the ordinary PC but as difficulties of mining increased mining became impossible using PC. Right now, you can buy specific equipment made just for mining and they can be expensive (though you can recoup your investment easily since Bitcoin is rising in value). Now, with PC I heard that you can instead mine other coins. Just search for it somewhere in this forum or in Google for more information. Mining business can be a good way to earn some money especially if your source of electricity can be cheap.