Initially mining will consist of sucking up surface dust.
Our planet has differentiated its component ores thermally, so that we have a crust, mantle and outer & inner cores. Asteroids are composed of a more homogenous mix, and this means they are rich in platinum group metals. The platinum would be worth recovery to Earth.
It is suggested that future historians will see this as the beginning of the paramount industrial revolution.
What's this? Why, it's the Hiller Flying Platform! It flew in 1955.
It seems to me that asteroid mining is the only space activity (beyond satellite communications) with even a remote chance of a return on investment. Exploration of Mars, on the other hand, is a financial black hole. Dreams of humans becoming a space faring civilization will come true far faster by mining asteroids than trips to Mars.
I now return you to your regularly scheduled programming...
The key here is that US now included in their law celestial bosies... So mining is allowd, and what counts is "who gets first there". It is bad because US is like owner of whole space... It is good, because now a LOT of private space projects can go live without any law issues. Race to space - here we go! Who gets forst there will have full rights to it (according to US law)