Adding owner to reduce Home Sale Tax on capital gain

[Issac Kao]

I plan on selling my house to downsize and move out of state. If I sell the house now the capital gain would be around $700-800k. Being married, we would take $500k off that gain, with still a decent chunk left. I've read online that you can further reduce the capital gain by adding others to the ownership. My son just turned 19 and have lived with us in this house for the past 8 years. If I add him to the ownership right now would he be considered for the full $250k single reduction or would I have to wait two years to qualify for the full $250k?