Please help - Marriage or not?

I have 2 Questions: My man & i want to get married but are not financially stable at the moment, We've told the family we'll wait for 2yrs. Our religion says that if we sleep together we're already married. So we want to get married in God's eyes. Ques 1 - Do we exchange vows just the 2 of us or do we need witnesses? Ques 2 - Should we wait or can we get married.