With all due respects, we don't give free legal advice on this forum ;D ;D ;D, it is really worth exactly what you pay for it . You should really consult a tax specialist or the IRS regarding the particular facts and circumstances in your case.
That said, the general rule is that if you have lived in your home for 2 out of the last 5 years as your primary residence you do not pay federal tax on the first $250,000/$500,000 (single/joint return) of gain. Do not know what the state of Washington does.
It used to be you had to roll over your home sales into another home and then you could get a one time exemption from taxes after you turned a certain age. But after Clinton, no longer. I know a number of people who keep building homes, selling them, and making profits on tax free sales, as long as they follow the two year rule.