Isaac Pennock offered to sell Charles and Rebecca the Brandywine Iron Works. Although Charles declined Isaac’s offer of sale, he agreed to lease the property for $420 a year, which at first appeared to be a low price.

In 1817, Charles and Rebecca's family moved to the old Coates homestead, Brandywine Mansion. Rebecca noted that “everything about the Brandywine Iron Works, including the house, mill and farm was in a wretched and forlorn state. The mill was hastily built, and the harness could not take weight of necessary castings.” Rebecca told her father that it should have been put in repair before they came. Isaac replied, “what you are doing now will make it so much the better for yourselves — for when I am gone this property will be yours.” That was the incentive for the young couple to rebuild the mill, adopt new technology, and buy new equipment, which allowed the site to produce a higher quality of iron.