I'm (ahem) about 175 and I can climb to the top of a Cherubini Hunter 25' fwiw.
"Hull rot" isn't an issue on anything but wood hulls. Blisters and bottom problems are issues sometimes, but there is a wealth of info out there on that. Decks can go soft depending on water and construction type/material.
Check out as many sailing marina's lending libraries as you can - they are usually stocked with good books on all these topics you can borrow for free (make sure you return them). Talk to sailors on their older boats in marinas and gain some real world insight as well. Best of luck!
EDIT: My old boat was actually quite cheap to refit, other than the expensive bolt ons I just had to have. Had I not bought all the high ticket stuff, it'd just been epoxy, fillers and the hours upon hours of my labor. The biggest cost other than "stuff" is time (which I thoroughly enjoy, as I have come to learn I love working on boats - but not everyone does)