They assume control of the property, this is how America has kept most of south/central America dirt poor, but basically they went in to place without infrastructure, lets say electricity, and they say they will build that for them for XXX millions of dollars which the country has to begin paying in X amount of years and they have 20 years to pay it back . They make promises like hey soon as we build this for you will see changes, your economy will boom and you'll easily pay the money you owe us. The get the electric system built, they'll even train some of the natives but for the most part they really run it. Year 1 of payments is due and you don't pay, all of sudden your electric company now has issue, power starts going out, people are unhappy etc etc.
End of the day what happens is they literally either destroy or cripple what they built or and what is most likely to happen here in Africa is they take over and reap any and every economic benefit from what they built (use roads they built to flood the market with Chinese made products, use ports and airports to transport things around the world etc)
if you want to know exactly how it will go , get this book