What you mentioned is true for Mr Custis and his planatation. However, be careful not to suggest that most others were like this. I for one wouldn't think so. Slavery was part of a system designed to earn a profit, and few Southern slaveholders behaved as irresponsibly as Mr Custis.

By all accounts Mr Custis was lazy and disinterested in the management of his property. Mr Custis spent his time writing bad poetry and plays. As a result Arlington was heavily in debt. Lee as executor was saddled with responsibility for covering his father-in-law's insolvency.