I don't know any other than after rebuilding 2 outdrives, and replacing 2 engines myself on mine, I like to think I know more than I did 5 years ago...
looks like a nice boat, but I'd start with the basics after a water test.
I'm told the 496s are desirable engines due to their durability. Looks like closed loop cooling on them as well. Are the exhaust manifolds closed or raw water cooled?
on the trailer can you physically wiggle the drives up/down at at all? or are they solid against the gimbal housing?
when were the raw water pumps/impellers last replaced? spark plugs? engine computers read? hours? test everything that has a button. trim tabs, drives, shifting, A/C, generator, etc. last oil change?
how clean are things? windshield well attached? anything loose?
that's a good chunk of change, so I'd expect that boat to be damn near perfect at that price point... I paid about $30k for my 292, but it was in BEAT shape. (and 2 engines later is closer to 40k now).