No plot, no base. You rent a plot in a settlement that has an owner, with the title matching the district tier. Since Nov 4, tier 1 plots are paid for with a title, not with money.
Land Plot Title: buy $100,000 · research $50,000. A title to rent a plot in a tier 1 settlement (only if the settlement has an owner). Unlocks new items.
Land Plot Title: buy $800,000 · research $200,000. A title to rent a plot in a settlement in a tier 2 district (only if it has an owner).
Land Plot Title: buy $2,000,000 · research $1,000,000. A title to rent a plot in a settlement in a tier 3 district (only if it has an owner).
Settlement Title: buy $200,000 · research $100,000. A title to buy a settlement in a tier 1 district. The owner gets a plot for free, rents out plots and collects fees from tenants.
Settlement Title (II): research $500,000. A title to buy a settlement in a tier 2 district. The owner stays for free, rents out plots and collects a fee.
Settlement Title (III): research $2,000,000. A title to buy a settlement in a tier 3 district.
Eviction Right. Removes a player from a plot, along with everything they own; you can keep a part of it. It is used on the plot plan, after you have breached all of the base's security systems.