if you close on sale one year after the closing date of the purchase, the gain will be fully taxable as long-term capital gain. you are right it might all be taxed at 0% depending on your tax situation. if you sell it before then, the gain will be short-term capital gain taxable at whatever tax bracket(s) you're in. to get any exclusion it would need to have been your primary residence (it wasn't, your apartment was) and you would have needed to have lived in and owned it for two years out of five years before sale. based on what info you've provided, it doesn't appear you would meet any of the conditions for a partial exclusion. if you want an idea of where your taxes for 2019 TT has a free tax projection website - taxcaster.
