What old bills or coins have value?

Not at all. In general, old coins can be valuable because they're scarce or made of precious metals like gold, while newer coins are usually valuable due to errors.

As examples, some of the Presidential dollar coins accidentally were not sent through the machine that presses the date, mottos, and mint mark on the coins' edges. These so-called "smooth edge" dollars have sold for many times face value.

Similarly some 1982 dimes were struck without mint marks. These can sell for over $100.