My partner has Venus in Sagittarius in the 5th house, plus he's a Scorpio Sun & Mercury, with Leo rising, too. He's had a very difficult time in relationships because the Sagittarius influence causes him to need lots of space, freedom, and not be too fond of commitments.

Now, looking at your guy.......his Scorpio Venus could make him want to take some control over you. There could be a battle of wills. He could end up being jealous or possessive, which might turn you off. You may find at the beginning that you both have things in common, lots of sparks, but be wary of hints of power struggles to come.