did you charge the renters fair market value rent. if not it's considered personal use.
every year the expenses should have been prorated between rental and personal use. the rent and the portion of any mortgage interest and taxes related to the rental should've been reported on schedule E each year and were not limited (except by the passive activity rules) other expenses you paid and depreciation you should have taken would be limited to any remaining gross income and be carryforwards.
failure to report the depreciation could result in underpayment of taxes if the taxes you pay on the capital gain are less than the takes you would pay on the depreciation recapture.
court case. taxpayers received $500monthly rent for house rented to parents. all use was personal use since rent was less than fair market value. those no rental epsnes were allowed but the taxpayers were required to include all rent received in gross income (Jackson TC Memo 1999-226)
your choices are to wing it or consult a tax pro to discuss what should be done for the year of sale.
