About to buy a 1989 Catalina 27. Need advice

[Xavierp]

I am a medium level sailer and sail hobby Alcatraz and 16 and lasers. I want to get a 26-28 feet boat now.

I saw a decent 1980 Catalina 27.
The owner rarely uses it once or twice a month.
It s mooring

1- there is a strong smell of oil mixed with diesel inside the cabin. Of course ventilation will help but how to figure out where it comes from. I didn’t see any obvious leaks in the engine compartment and no residue of oil and diesel at the bottom.
2- quite a few spiderwebs on the deck…
3- cracks as well
4- soft spot when stepping on an area
5- There is water one inch or two at the bottom of the port storage compartment under the cushions inside the boat Picture#4
Any idea where it could come from?
6- the engine…. Hie do i know if it’s working properly? It sounded good to me as I’m not used to boat engines

Thanks all