I started a real estate website for my country and to quickly add content I copy/ pasted a lot of real estate offers from other sites.
Now, I did not inform anybody of the other sites of this, but is that illegal?
If yes what are the worst consequences I can face?
That particular copyright violation will be very easy to prove damages for since each property will have a particular commission that the real estate agent asked to sell it expects to earn. That makes a court case far more likely in this instance with a claim perhaps running into the millions for lost sales.
No, it is not legal to copy information from other sites and paste it into your site, it is a copyright violation.
Copyright violations can be pursued by the owner against you. Consequences can be as little as them sending a cease and desist letter to them filing a court case against you.
When you say copy pasted offers from other sites, do you mean that you copied the content itself or replicated the offers for your own offerings? If you copy pasted physical content from another website, you are stealing, plain and simple. Taking content that doesn’t belong to you and using it for your own commercial gain is a pretty serious thing to admit too. There is no question whatsoever that such actions are illegal and could be pursued.
In regards to the worst consequences, with all criminal offences you could get anything from a cease and desist or takedown notice (legal letter demanding you remove everything you took), you could be pursued via the courts for damages, legal costs, compensation (which could - depending on the level of the theft run into thousands) and if you were outright ripping other people off and caused them a serious loss of business (which could be the case) there is always the possibility of serving jail time (though for this kind of thing, it would be very rare). And as you’re in a different country from them… you could be facing an international lawsuit.