What is Cryptocurrency Mining?
Simply put, mining is the process of creating new coins (that did not exist before) by running specialized software or hardware. (Unlike staking or trading which is moving existing coins from one party to another). I do not endorse any of these projects, while I found them worth attention. Always do your own research before investing.

Bitcoin Mining
You can buy 2.7 Th/s for $99, and you won it forever, no subscription fees, no electricity cost involved. Two years ago ROI was 6 months, meaning you would get your money back in 6 months. But the hashrate of the bitcoin network itself is increasing, and so your earnings slowly decreasing even with BTC price rising. Whenever you read this, and decided to use it, please open ChatGPT and ask it "How much BTC it will mine with 2.7 Th/s", and it can predict how long this thing will be giving you any money. The bottom line, it will give you some money for few years only. It does not work with every wallet, so you would need to get Speed Wallet.