I want to know if someone want to transfer their money from foreing country to usa will be legal ? And if so how much money to IRS I have to pay for ?

Yes, it is legal to transfer money to the US. No taxes are owed on transfers you receive.

Please verify for me - the transfer you are considering is from someone you know and trust, right? Be aware that there are a lot of scams out there regarding international money transfers, so take care. For example, see:

Scams: Money Transfer