What are the typical build area sizes that DLP 3D printers use?

This depends a lot on the output power, desired resolution and setup the printers use. The most common build envelopes in the XY plane range from approx. 50x40mm to 100x80mm. This for off the shelve DLP projector printers with no image shifting and XY resolutions between 0.025 to 0.1mm.