Duncan's Bride (Patterson-Cannon Family 1) by Linda Howard

Reese Duncan lost half his ranch and all his dreams to his ex-wife, so when it came time for a family he did the logical thing: he advertised for a bride.

She had to be willing to work, to bear his children and to settle for lovemaking in place of love. It sounded perfect... until Madelyn Patterson arrived. 

One look and he had to have her. Never mind that she was New York and nightlife to his own plain-spoken Montana ways. She was willing to herd cattle, wax floors and bake biscuits by the dozen. She was even willing to bear his children - but at a price he couldn't pay. She wanted love... and he was a man.