Because you acquired the home by a gift, your basis usually is the basis that your parents had in the home (what they paid for it, plus capital improvements they made over the years). It may be difficult to reconstruct this information, but their initial cost may be available (e.g., published on Zillow).
Return filed by a married person who does not file a joint return. Filing separately may save taxes where each spouse has separate deductions, but certain tax benefits require a joint return.