Building trust for a freelancer is hard, especially one working remote with little on-site. Transparency usually helps in these settings.
I've had to work on projects as a freelancer where there simply wasn't much progress for weeks because they were such monstrosities, that trust and a prose-documentation of my work was the only thing keeping me afloat. (think 5 different languages talking to each other via SOAP, consuming 3 different databases, all with encoding problems between every possible step)
Just being able to point at all the screenshots from the bazillion different debugging windows, log diffs, etc. would have made things much easier back then. Swapping me out for someone else two weeks into this project would have been a terrible mistake, but besides my assurances and some prose the manager had to trust me. Bad for him, bad for me.