For many years I have collected about 100 such words.
There are at least two types of homographs. Most frequently encountered are Type 1, in which words of closely related meanings perform as different parts of speech when pronounced differently.
Carley, James F.
"English Words Spelled the Same but Pronounced Differently,"
Word Ways: Vol. 46
, Article 17.
Available at: http://digitalcommons.butler.edu/wordways/vol46/iss2/17