Assalamualaikum ,one of my friend said to me don't invite the shia in house and don't go to them because they are not muslim.and said this is hadeeth as far I know shia was not at the prophets time.

Any person who believes in oneness of God and affirms that Muhammad is the last prophet of God is Muslim. All Shia Muslims believe in this, that's why they are as good Muslims as others are.