The following are things I shy away from, or at least, give a good long look into:
Fuel bladders in doors; bed liner; frame mods; factory suspension mount locations being modified or removed; rust; newly rebuilt engine, tranny, t-case, etc with low miles after, extra wires under the hood- are they cleanly and semi-professional looking, or look like something a tweaker would do; fresh paint (chassis or body); engine cleanliness and parts (aftermarket vs. OEM), excessive sludge/greasy parts, or missing major parts (seats, doors, roof, etc).
The above is regardless of make/model. I expect a certain amount of shade tree mechanics in an older vehicle, however, I don't want someone else's gremlins. A rule of thumb I use is checking out the interior first, as, if it's trashed or mismatched, it likely translates to other laziness in regards to maintenance. That said, I bought my cruiser knowing it needed work, and it had several items on the above list. However, once i talked to the PO, I realized he was pretty good with mechanical, but not so much the cosmetic, but that was the extent of his modifications.