Kidco

Kidco is a movie starring Marty Van Hoe, Scott Schwartz, and Mahlon Richmond. Kids who live on a horse ranch decide to sell the excess manure as fertilizer, but their new company soon comes under fire from the state tax board.
A boy who lives at a country club where his father works decides to make some extra money by selling composted horse manure as fertilizer, and has his three sisters (two of which are older) join him in the enterprise. As their sales increase, they draw increased scrutiny from the IRS and state tax board, as well as the large scale competitor who seeks to put them out of business at any cost.