He's just 'building castles in the air' if he thinks he can open a restaurant without any money.
Millionaires built their 'castles' along the lake.
(..) Did he now... Nice job? Easy? We've been hunting Horcruxes. And we think the last one's inside the castle. But we'll need your help getting in. Which job my brother has given you no, it's a suicide mission. Do yourself a favor, boy. Go home! (..)2011 Harry Potter and the Deathly Hallows: Part 2
(..) to make sure we don't find the rest. And there's more. One of them is at Hogwarts. What? You saw it? I saw the castle. And Rowena Ravenclaw. It must have something to do with her. We have to go there, now! Well, we can't do that! (..)2011 Harry Potter and the Deathly Hallows: Part 2