It is just a scam. You can mindread him to find this out, and also learn the location of his stash (though I don't think the experience points are worth getting a couple hundred extra gold).
That's what I thought. I told him no thanks last time but he came back again. I just wanted confirmation before telling him no again and losing out on a quest.
You'll meet him one more time, but unfortunately you don't get to slap him around. If you pay him in either of the first couple encounters he'll ask for more in the next, claiming to need money for permits or bricks.