the general rule to exclude gain on the sale of your principal residence is that 2 (any 730 days) out of 5 years prior to sale you must have used it as your principal residence. if it were sold today the 5 year period would be 6/24/14 through 6/23/2019. since you say you moved out in 2015, it would be impossible to meet this rule. in addition you say you rented out your portion. any depreciation that you took or should have taken during the rental is subject to recapture upon sale (not eligible for exclusion)
having said all this, you might be entitled to a reduced exclusion if you moved out for change of employment, health, or unforseen circumstances.
if you want to use new employment to qualify for a partial exception, there are 2 rules you must meet
1) the change occurred during the period you owned and used the property as a main home
2) the new place of employment is at least 50 miles farther from your home than the former place of employment was. if there was no former place of employment, the new place of employment must be at least 50 miles from the home sold.
