I'm going to buy expensive antiques at a yard sale for a cheap price and the owner had no idea of its value
How will you know if the items are valuable?
Don't worry about it I'm an expert on antiques.
It's frowned upon to profit off the ignorance of others. You should be honest with these people and let them know the real value of the antique they're selling. I'm sure they'll be grateful for your honesty.
It's not stealing, it's making me wealthy by doing nothing.
You cannot expect to be wealthy without doing anything. You should work hard to earn money. That's more satisfying and the moral thing to do.