Independant consultants are advised to bill on
value-added. So for example patio11 consults on how to improve the conversion rate of visitors to a site. Using his light grey arts, he can go from 2% conversion to a 4% conversion. For a site turning over 10million a year he has just made them an extra 10 million a year.
So he can charge commensurately.
The question I would ask you is how does your prospective employer charge? Are they just billing hours and charging?
Are they delivering projects that have clear value outputs like patio11? Is their profit related to the number of hours you work (bums on seats), or could you do a days work and move them from 2-4% conversion as well?
Now ask how does your prospective employer make its money - usually they charge the client X and pay you .6x and pocket the difference.
Their risk is not having projects to charge X and still paying you .6X.
So - you could do three things
1. take the usual salary of X - employee consultants tend not to get paid much differently to actual employees - so try glassdoor.
2. Are they open to you taking on risk - that is can you get .9X for the willingness to get 0X if no projects come in the door? You are then a freelancer, and they simply find the jobs.
3. Are you willing to take on that risk? If so you probably dont want to be an employee