Oh I feel your pain. We have a free-form "Occupation" field on one of our main Sales applications, so I've just spent weeks building a lookup table to make some sense of the thousands of mis-spelled and misleading entries.
My particular favourites are "HR Minger" - I can only assume they meant "HR Manager", and the eighteen different spellings of the word "Childminder".
For some classifications, like occupation or geographic region for example, there are standard coding schemes. After mapping and re-coding user entered free form descriptions to the standard coding, then there are more possibilities for doing stuff like cross referencing sales data with 3rd party marketing databases.
"The universe is complicated and for the most part beyond your control, but your life is only as complicated as you choose it to be."