13:17and he provides that no one should be able to buy or to sell, except the one who has the mark, either the name of the beast or the number of his name.

and he provides that no one should be able to buy or to sell, except the one who has the MARK,

The MARK will be necessary to do trade. Consider that at this time, the world may have very little food. Previously there was drought (Revelation 11:3,6), famine (Revelation 6:5-6), and total disruption of food production (Revelation 6:12). NO SUN, NO FOOD!

So it is likely that the official economies of the world have broken down (see lament in Revelation 18:11), and the only thing left is the "underground market" controlled by the "earth beast". How appropriate that he should come "out of the earth" (verse 11).