Hi marylander,

Opening a third card should have a very minor effect, especially since it appears you have opened no other new lines or in the past several years.

If you know what card you wish to add to your portfolio, I wouldn't hesitate to add that one promptly. Better now than within six months of the time you wish to buy a home. (Even then it probably wouldn't hurt you enough to matter...but the way that underwriting standards are tightening as we speak, applying now may give you a better chance of being approved than applying later.)