Marriage at a Price (2009)

Blurb:
Courtney, a young horse farm owner, is glammed up to mingle with high society at a racecourse, hoping to find an investor for her business. Socializing with the rich, dolled up in a frilly dress, puts tomboy Courtney out of her comfort zone, but she has no choice. She has to find a way to repay the debt her deceased mother left her. She meets Jack, a mysterious man who seems interested in investing, but she had no idea he would come to see the farm for himself. Spending days with this handsome man, under the same roof . . . ?

Source: www.anisearch.com/manga/24856