Do not offer a free word-count service for potential clients who are not even sure if they will be giving you the job or not. Instead, give them your rate per word and let them handle the word-count and eventually how much the project would cost them. I’ve learned that the hard way.
It is a complete waste of your time to wait for the potential client to send you the material so you can in turn do the word count (in case that is doable, of course. Some files cannot be converted, e.g. images), and then give them a final quote, only for them to find it too high or to find your time frame not suitable.
Existing clients can of course benefit from this service; at least mine do.