Exemption for Capital Gains taxes

I am single and have a 3-unit house that I have owned, been renovating, rented, depreciated, and lived in for 20 years. I am planning to sell it this year. My accountant informed me that I will have taxable capital gains income of around 250k from the sale and that I can avoid federal capital gains income taxes from the sale if I make less than $25k ordinary income this year. I think I heard you say before that there is an exemption of capital gains if one makes less than around 40k in ordinary income. I tried raising this issue with my accountant to which he responded angrily “don’t tell me how to do my job!” Can you please clarify? What is the limit in ordinary income that I can make this year to exempt (not pay taxes on) those capital gains taxes from the sale of my 3-unit house? I don’t plan to have any other capital gains this year other than from the sale of the house. Thank you.