I friend have received a proposal from a company there and I would like to help him. We are already aware that company hold 30% until it check if you has a degree and stuff and can hold it forever if it concludes your degree is not enough. But what about cost of living and taxes? What would be the net salary after taxes? Any advice?
You might consider "good" to be "relative to what other people at your level might be earning", but relative to cost of living and taxes to support a single person, €4.700 is very good, and your friend should be able to easily get by.