How exactly does the money making process work? You buy some cryptocurrency for a certain price then sell it for a higher price and the difference is the money you've made? This would mean that the money you've made is still in terms of cryptocurrency. Then can that money be converted into the whatever kind of cash your country uses? How does it work?
what you are describing is trading, some people do trading to accumulate more and more bitcoin, and then when bitcoin hit for example 1BTC = 20k usd, then they withdraw it to USD, so that's how you make money.
but trading will be risky and you might lost you coin, so be aware if you wanna do trading.
another way is you buy in some coins let's say 1BTC at 10k usd, and you do not trade it and just hold for 3 years, bitcoin rises to 1btc to 30k usd, so in two years you have earned 20k and you withdraw when you want it. BUT there is no guarantee that you earn in two years, if let's say you but an alt coin, it can crash and dissapear.
BITCONNECT is very good example for crashed. it once go up to 4xxusd, but bitconnect shut down and it's now lower than 10usd and so many people losing their money.
so u need to do a good research about the coin you wanna hold.