Here is Wiley's excerpt on sec 179(it says 510K for 2017 lol)
Section 179 Election—
There is a Section 179 election to expense a limited amount of tangible personalty if used in a trade activity. It is not available for income-producing property (i.e., rental property) or real property (i.e., real estate).
Note that Section 179 expensing is taken into account before bonus depreciation for years that permitted bonus depreciation. Off-the-shelf computer software also qualifies under Section 179, as does qualified leasehold property, qualified restaurant property, and qualified retail improvement property. Air conditioning and heating units also qualify.
1.The maximum amount expensed in any year is limited to the lesser of business income or $510,000 for 2017 ($500,000 for 2016).
2.The Section 179 expense cannot exceed the income from the business, reduced for all expenses except Section 179. Any election to expense in excess of the business income limit is carried forward (indefinitely) and used in a year when income is sufficient.
3.The Section 179 election is phased out (dollar for dollar) if qualified assets purchased exceed $2,030,000 for 2017 ($2,010,000 for 2016).
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