When you mine, you generate coins and getting income paid by the coin you mine. Some pools like NiceHash will pay you in Bitcoin no matter what coin or token you mine.
Now what do you do with those coins? You have a few options...
HODL - Hold your coins in a cold wallet and never sell until the value of your coins reach the price of a Lamborghini supercar. This strategy is the safest because you are the actual owner of the coins and nobody can change that. Just don't lose your seed keys :). By the way you can HODL for any goal or HODL forever or to give it it to the next generation - it's up to you.
SELL - Some miners are not interested in investing in cryptocurrency, so they simply sell their coin after certain amount has been accumulated. This method is also pretty safe as whatever the current value of the coin is, determent how much you will get. You can also pay for expenses like electricity and spare parts with the cash you get. The downside is that YOU PAY FEES to sell your crypto. I recommend using Coinbase Pro to save money on fees and only pay about 0.05%. If crypto went up and you sold before that, you lost, but if you sold high and then crypto went down, then you won. In the long run it's easy to see the trend of crypto generally goes up. So if you patient enough, not selling usually is the best way to go.
STAKE - This method require you to put your coins away for while - the longer the better. You could do it the hard way and create your own node, depends on the coin, stake the minimum amount of coins (usually require many many coins) and you will get rewarded to do so. It's also called PROOF OF STAKE. You can also use third party companies that will STAKE your coins for you with an APY as a return. For example, BlockFi offers 4% APY (variable) for your BTC and other coins. Nexo.io offers up to 12% APY if you are willing to get paid in their Nexo token as the reward. Some other requirements needed to reach this high APY with Nexo. The downside of staking with a third part is that YOU DON'T own your crypto - they do. If something happened to your coins or if the company bankrupt - you might lose your whole portfolio. This is a low risk in my opinion because those companies are very large and offer some insurance against your crypto. Even the popular Coinbase offers some stacking options for some coins.
*The links to the companies in this post also offers $10 free if you deposit $100 and also benefits BitcoinMerch.com.