What are pros and cons of adding girlfriend to Home Deed? We are not married and a few years away. Is thsi in my best interest?

The con is she becomes half owner of the house, and if things don't work out, she owns half of your house.  Im not sure what a pro would be other than the gesture of showing your commitment.  I know married people who don't have their spouse's name on the deed, as the house was a pre-marital asset.