There is a practice that many do, which is to buy and sell, as they do in localbitcoins.com, they buy low and then sell high, generally this works wonders in countries with inflationary economies, from a point of view of Saving is quite beneficial, because the money in local currency increases as time goes by, sometimes in a day you can earn a lot of money, but you must do the transactions very quickly so that it is not dangerous to lose.
Actually these trades yield a massive amount of income but only if and once you become a recognized trader and know how much fees you have to pay on each trade as taxes to the government and making sure you are doing it legally.
I have seen the variance in buy and sell on localbitcoins is easily around 5-8% on average in buy-sell and once who buys from users earns like 8% on buying trades and then 8% on sell trades, all he needs is a good reputation and a genuine setup but it is not as easy as it sounds though because I myself tried this and people are really smart and try various methods to scam you like fake messages, fake transactions and even carded funds.
