SEO Reseller Services - concerns

Hi

I've been providing some basic SEO for a client I know well. I would now like to scale. The obvious route seems to be to use an SEO reseller service.

However, I would like to know how people in this position manage the security and trust aspects of the relationship.

At the moment I make sure to perform backups, only make changes that are appropriate and beneficial in the long term, I take proper security measures with the client's WP login details etc.

If I was to operate under an SEO reseller model then I'm entrusting someone else to act with the same due duty of care with the client's website. How can you be sure that the SEO reseller is not giving out the login/pw details willy nilly, taking appropriate backups, not engaging in anything that might damage the client's reputation, doing only white hat SEO etc etc??

Also, for those of you providing SEO via a reseller - are you upfront with the client that the work will be carried out by a reseller? I'd imagine the client's immediate reaction would be to simply go direct to the reseller and cut out he agency fee.

I'm curious to know how digital marketing agencies operating under this model overcome these issues?