Good article! However, I don't think that the ROI for bitcoin mining is 3-4 months. Even if that is true, you need to compare that with alternative costs. Such as just owning bitcoin during that time frame.
If you already own bitcoin, I would recommend margin funding (only if you are aware of the risks). That and other interesting ways to make money with BTC is summarised here: https://cryptorunner.com/bitcoin-finance/ Another option is affiliate marketing which is not mentioned in that article (they make money that way).