2001 is pretty new, still some fairly rapid "depreciation" in there.
It may be that aircraft prices are headed back up after 3 years of
declines, we shall see (depends on the economy). If they do, then the
appreciation may well outperform the depreciation due to use. 1200
hours is midtime, and if you put 500 hours on it it will be at high
time of 1700 which is a harder to sell point, but can be done if you
lower the price. If it is the airplane you want, has the avionics you
want, it may not be too bad a deal, certainly better financially than
buying new. In 500 hours and 5 years you will spend $20000+ fixed
costs (hangar, insurance, annual) and $20000 in hourly costs, so and
extra $10000 in depreciation one way or the other is not going to be
all that signifigant, then again its not chump change. For getting
your ratings, I can hardly think of a better trainer.

I think this is a good time to buy, as the market seems to have
bottomed. A 172 is a great airplane. Go for it!