I just bought a house with cash, fixed it up, what if i sold it within 6 months, how much would i be taxed?

Lt me preface my answer by saying you should always consult a qualified tax professional. that being said..

Since it's not your primary residence you can't take a deduction for it anyway, so there is no difference if you sell it today or 6 months from now. The only way it would make a difference is if you lived in the home as a primary residence for 2+ years. Then you could deduct $250,000 (as a single) on the tax of capital gain you would be claiming.

You will also need to pay a realty transfer fee in New JErsey. You can calculate the exact cost on the sellers page of http://www.justjerseyrealestate.com. Good Luck to you.