Well, i suggest you, most of the sites are scam, But not every site, and if you want to invest your bitcoins into any cloud mining site than only search about it and may be your friends are doing it than you take help from them, and if you get trust-able mining site than in the start invest your litter amount.
yes it's true that currently is very difficult to find real legit cloud mining sites but doesn't mean all of cloud mining sites are scam but just be carefull to those sites which is offering big profit to their investors because usually they are scam and as far as i know that legit cloud mining sites only offering small profit for their investors but for long term only
They are a scam one way or another because their business model is flawed. If they were able to profit from mining themselves why offer contracts to people? Why not mine for themselves and take all the profit?
The answer is simple: they can take more money from you than they would be able to mine. You will provide them with a loan, they will have the cash in hand and won't have to wait a year until the miner does its job and if something goes wrong they can always run and you'll be left with nothing.