A used tandem with flat bars for both of you could be a good starter.
Do not advise a department (W-mart, etc) type tandem.
Trek and Burley have several models in the configuration you look for.
If stoker does not want flat bars, it would be easy to put on a set of drop bars.
Hauling a 100+ lbs non-pedaling friend could be a bit of a challenge if you start encountering some hill work.
Good luck!
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