There is a unit for sale in the Princeton Co-op on 15th in Capitol Hill, immediately south of Howell. It's a remodeled top floor unit with green features, such as low VOC paint, bamboo and cork flooring, and a small energy efficient dishwasher. For more info, click here.
And the asking price is totally reasonable: $205,000. There are also links to the specialty banks that do share loans for co-ops.