The estate covers about 51,800 hectares, or 128,000 acres, in 19 counties. Established in 1337, it currently has about 700 agricultural lettings, including about 300 whole farm holdings made up of a farmhouse, land and buildings.
The Duchy said the proceeds from the property and land sales would be invested over the next decade in local communities, affordable housing and environmental projects.
A spokeswoman told the BBC the Duchy could not confirm how many tenants would be affected by the sale plan. She said the estate was engaging with people directly and"supporting them through the process with care and respect".
"We recognise that each of our tenant's circumstances are different, and we are taking a careful, case-by-case approach,"the Duchy said.
The BBC was told there were"no cliff edges"on immediate evictions and that the Duchy was working closely with every tenant to find a suitable outcome.
The prospect of a permanent break has already unsettled some families."Once a family is told that its long-term relationship with the Duchy may change permanently, that uncertainty lives with them 24/7,"one man told the BBC.