The minimum requirement is historical transaction data with three components: object characteristics (what was valued?), offer prices or estimates (what was expected?), and realized prices (what was actually paid?). Depending on the industry, market data, time series, and external data sources are added.

The real preliminary work lies in data cleansing and feature engineering: removing outliers, resolving inconsistencies, deriving meaningful features from raw data. In most companies, the necessary data already exists. What's missing is not the volume of data but its systematic preparation and use.