We just bought a house 3 month ago and now I have to sell my new house due to job transfer. Does anybody know if I need to pay any extra penalty tax for selling my house within 2 years of purchase? I am sure I won't gain any since I have to sell the house so soon. Thanks in advance!

There is no penalty. But you need to pay tax on any any real estate gain (selling price - purchasing price). In your case, you probably won't have much gain. You will lose $$ on paying all the fees to realtors.