a neighbor is selling a cedar strip Reliance double for a client of his.

Mike:
I'd be reluctant to sell a non-rudder tandem, unless the buyers were very experienced paddlers who knew what they were buying. For beginners (who are the likely prospects), it could be an 'accident waiting to happen'.
I'd also want to know (with testing) whether the double would float high enough when swamped - some designs have such small compartments and large cockpits that they won't get the coamings above the water surface so are impossible to pump.
The 'Deep Trouble' books have some information about double kayak 'accidents'.