Agnihotri had her first modelling stint at age 10. When she was a teenager, her father relocated the family to Madras, Tamil Nadu because of his job. There, she attended Good Shepherd's Convent School and acted in a school play. Bharathiraja, one of Tamil film's prominent directors, was in the audience and was searching for a heroine to star in his new film. He met with Rati's father and promised the film would wrap in a month. Her father reluctantly agreed, and a sixteen-year-old Rati was very excited to star in her first film, Puthiya Vaarpugal (1979).