In the typical circumstance, the trust became irrevocable when your father passed. As a result, the trust took the house with a stepped up basis (stepped up to its fair market value on the date of your father's death).
You would then subtract that (stepped up) basis from the sales price (less selling expenses) to arrive at any capital gain (or loss).
If there is a gain, then the gain will be taxed at the trust income tax rates unless the gain is distributed to the beneficiary(ies). With respect to a gain, it makes no difference whether the property was held for personal use or for investment; the gain is taxable.
