Sir William Lucas, desp[ite having a title, was unable to give his daughters a sufficient dowry to enable them to marry well. The family, with its numerous children, really could not afford to support unmarried daughters, and the daughters themselves could not get jobs without losing their status at gentlewomen. Charlotte, at 27, was considered nearly beyond marriagable age, when she received the offer from Mr. Collins. Given the economic situation of her family and her age, accepting the offer was the only possible way she could avoid being an economic liability to her family -- she had no other economic oppportunities. She herself sees the practical necessity of the marriage, and unlike the more romantic Elizabeth, decides to make the best of Mr. Collins.