If you have a considerable gain, in a principal residence and you rent it for more than three years, it can lose the principal residence status and the profit must be recognized.
Section 121 provides the exclusion of capital gain on a principal residence if you own and use it as such for two out of the last five years. This would allow a temporary rental for up to three years before the exclusion is lost.
Let’s assume there is a $100,000 gain in your principal residence. If it qualifies for the exclusion, no tax would be owed. If the property had been converted to a rental so that it didn’t qualify any longer, the gain would be taxed at the current 20% long-term capital gains rate and it may incur a 3.8% surcharge for higher tax brackets. At least $20,000 in taxes could be avoided by selling it with the principal residence exclusion.
Depreciation, a tax benefit of income property, is determined by the improvement value at the time of purchase or at the conversion to a rental whichever is less. If the seller sold the home and took the exclusion and then, bought an identical home for the same price, he would be able to have 60% more cost recovery and avoid long term capital gains tax.
It is always recommended that homeowners considering such a conversion get advice from their tax professional as to how this will specifically affect their individual situation.