Re: What would you pay?
If everything runs fine and the boat is in good shape, $2k is reasonable for it.  A '73 is an OMC electric shift Stringer Drive.  OMC's been outta' business for over 10 years and they stopped making the Electric Shift around '77.  It's a decent drive, but it'll require attention.
I'd say pass, unless you're familiar with the drive.  Most mechanics I encounter won't even look at it.
Welcome aboard.