the 100K is considered capital gains.
But I need to know more about this:
1. You mention that you had no rental income for the past two years. Was this a rental property, and have you reported rents and expenses on schedule E? And even though you had no rents, did you continue to file schedule E for the past two years?
2. did you live in the property as a PRIMARY residence for at least 2 years of the past 5 years? The time spent in the second home to meet this test did not have to be consecutive. You can total months lived in over the past 5 years to come up with 2 years of qualification.
Yes, you will have to pay capital gains of 15% on the 100K.
But acutally your capital gains may be less.
The formula for capital gains in your situation would be:
Capital gains = sale price (FMV of home + 100,000) - (original cost of home + improvemens and additions, + major repairs, + closing costs not deducted else where from when you purchased it, - accumulated depreciation from your rental periods) - cost of selling or trading the property.
NOTE: there will be a small recapture tax of 25% on the accumulated depreciation for the rental periods of the property.
ALSO NOTE: major repairs are those thanks you fixed or replaced that are intended to last one year or more. Such as replacing shingles on the roof, or bathroom tiles, etc.