Tax implications of a single flip

[David Baker]

Hi all, I have read several posts on first flips and taxes but have yet to find the answer.  So here goes!  

My wife and are both employed and in a higher tax bracket.   So if I flip a house this year and profit $25k am I going to have to pay at my current tax rate plus self employment taxes or just my current rate (assuming it doesn't bump me up)?  Sorry for the run-on sentence.  

And a followup when does one have to start paying self employment taxes?

Thanks!