I am unmarried and I own (no mtge) and live in one unit of a 3 family house; Although the house is a legal 3 family (with 3 separate units, meters, utility lines etc), I've "never rented" out the other 2 units; I've always occupied the entire house. I plan to sell and buy a one family house. A potential buyer will pay me $1,000,000.00 for the house;

1. How do I go about determining the basis of my home?

2. Assuming the basis is zero, (The house was built in 1931 by my grandfather and has changed hands a few times over the years; Always transferred to another relative, never as part of a will or estate.) What portion of the sale price will I be obligated to pay Capital Gains tax on and what portion is exempt?

3. Would I qualify for a primary residence exclusion?