Answer:
We are going to be very close to making 150,000 this year and file joint marrried. If we go over 150,000 how is that going to affect our taxes?
== ans ==
It is very difficult to try and answer your Q because your lack of base understanding is clear.
First, I suspect your fear is you will at some point make money that puts you in a new "bracket" and therefore it isn't worth making. That can never happen. Someone making say 500K will pay the same tax on their say first 25K, 50K, 250K of earnings as someone who only had that amount of income. The tax rate is not retroactive to the earnings before it.
Also a tax rate is only applied to your TAXABLE income. Determining taxable income is the hard part of figuring the tax. It is (almost always) entirely different than what you may think of as income, and certainly different than say your W-2 says. First off, deductions timing differences and types of income are all in the consideration. Then a percentage is applied to that number.
The way to know your personal actual rate (which is different for everyone. even if they have the same job and pay rate), is to calculate the tax you pay (after defining what you mean by tax - Federal Income tax, with State taxes? how about Social Security tax, other types of "tax"??), and divide it by what YOU think your earning were. That amount will likely be different not only from Taxable Income (which is different for Feds than for State, and maybe then too for City), but by what your bank would consider. And on it goes!