The sale of you primary residence is tax free, on up to $250,000 of capital gains ($500,000 married filing jointly) IF you lived in it, as your primary home for at least 2 of the 5 years prior to sale.
You can only have one primary residence, for purposes of this rule. So, it kinda depends on the details of 50/50 and "I lived there 50% of the time''.
