Of course he's 'letting it slip' that he's just a Joe what fun would it be to wait until the end to tell these girls?
Letting it slip' NOW only serves as evidence that he's really, actually, in-true-life RICH!!
Now, Joe and the viewing public will get to watch certain girls make fools of themselves...and then Joe can make the educated decision that he needs to.
Think how hard it would be for some one wealthy to find some one 'into him' and not 'into his wallet'. What better way than to pose as an average Joe posing as a millionaire, who gets busted in week 3??