Under Section 121, you can sell your primary residence and exclude from taxable income up to $250,000 (single taxpayers) or $500,000 (married taxpayers filing jointly) in capital gains
A 1031-121 exchange allows the owner of, for example, an expensive house to use one benefit to exclude part of the gain from tax and the other to defer tax on the rest. And the gain excluded -- up to $250,000 for a single homeowner and $500,000 for a couple -- can be added to the "basis" of the new house, reducing the potential tax if it is sold.
The new break doesn't apply to all homeowners, only to those who have home offices, or those who convert their house -- or a portion of it – into a rental. The deferral applies only to the portion of the house used for commercial purposes. In general, you must use part of the home "exclusively and regularly" as your principal place of business, or exclusively and regularly as a place to meet or deal with patients, clients or customers in the normal course of work -- or for rental use. If you are an employee, your business use must be for your employer's convenience, not yours