There are lots of mining sites which gives free coins but you cannot withdraw. How true is this one? I cannot even withdraw what I mined. How to learn more from mining?
Those sites are a ripoff as they first give you free mining power and then ask you money to reach a certain level before withdrawal and most of the times you never reach that limit for making a withdrawal. This is a pretty great idea of ripping off people and it also works most of the times. If you are having your own mining hardware then mining would be pretty profitable for you but cloud mining is not worth the risk.