Are you sure that you will be eligible for the 20% deduction? I was under the impression that individual contributor / contractors type service jobs would not be eligible.
They are eligible if taxable income is below $157,500 for a single filer. $180K - $18.5K - $12K = $149.5K, so as long as other net income is below $8K....
So the proposed regulations, which appeared a while back, cleared up how this works. And it turns out, the principal asset disqualification, which is what I think we're talking about here, would not apply to OP's situation:
More information here:
How the Section 199A principal asset stuff works... but basically, this is only something celebrities need to worry about.
Note, however, that while the principal asset "disqualification" isn't an issue for OP's situation, the W-2 wages limitation may be. But an S corporation will fix that.
Also this comment: I would guess OP can save quite a bit of payroll tax with an S corporation and then quite a bit of income tax with the Section 199A deduction.
E.g., say the OP pays him or herself $80K in base wages because that's a reasonable compensation amount. If he or she also treats the shareholder health insurance correctly, that'll create maybe as much as a $20K nontaxable fringe benefit. The employer match for the SEP or 401(k) in this case might equal $25K (or 25% of the $80K plus the $20K).
This will maybe mean OP saves about $8K in payroll taxes via the S corp. And about $3K via the Section 199A deduction.
Note: I'm estimating the Section 199A deduction savings as 20% of the leftover $60K-ish of S corporation profit times a 24% marginal tax rate.