Katharine McPhee -- No More Rent Checks ... I'm a Homeowner!!!

Katharine McPhee has found the perfect home to celebrate her newly-found singledom.

The actress/singer -- who's in the process of divorcing Nick Cokas -- just dropped $1.4 mil on a house in Toluca Lake ... that's where Bob Hope lived.

It's perfect for a famous single chick ... 2,039 square feet, 3 bedrooms, big kitchen and very private pool and spa.

Katherine and Nick rented, so this is a big deal. The only other place she owned was a condo in Sherman Oaks that she bought with her "Idol" money..