Reducing Taxable Income - Shooting Myself in the Foot for a Loan?

[Mindy Jensen]

I want to reduce my taxable income as much as possible. (Selling stocks and want to avoid long-term capital gains.)

Maxing out the 401k is $18,500, standard deduction is $24,000. 

My question is, what does the bank look at when deciding to give me a mortgage? Am I shooting myself in the foot when I'm applying for a mortgage (primary residence, I live-in flip) by reducing taxable income this year? Or do they look at gross income? (It's been a while since I got a mortgage and things have changed.)

Asking here so others can benefit from the answers. @Chris Mason ?