If you apply for a credit card at Home Depot they will give you a 10%
discount (limited to $200). But what they don't tell you is, even
though you haven't even seen a statement yet, you must pay off the
purchase almost immediately. If you don't they will take back the discount.

As far as I can tell, there is no reason to have a Home Depot card
except for the initial discount. After that, Discover and some others
will give a 1% to 5% Cash back bonus.