I charge $25 per hour, which includes all my equipment and myself as an engineer (and co-producer if the client is interested). I may offer a discount for a block of time - and candidly, I often spend some of my own time trying to tweak mixes or try differnet processing
effects etc (simply because I want anything I work on/with to sound it's best.) I can also help the client with bulk reproduction, packaging, etc. - but I prefer for the client to do that on their own (too many headaches when the client is not satisfied wth what others have done).
Almost all my work comes from local word of mouth - however, I also have a decent web site, so once people are referred to me, they can go on the web site, see pictures of
the studio, a gear list and hear some audio files.
My studio is in my home - and I do not depend on
the studio for my sole income (it's basically a hobby which pays for itself) - so I am very selective about which projects I choose to work on and which people I trust to enter my home (this limits my earning potential, but also reduces risk and concerns).
As someone esle said - having gracious social skills (basically being a decent person), and acting in a progfessional and dependable way gets more work than an impressive gear lists etc. I've also gigged alot over the years - and I know being easy to work with and dependable has gotten my many more gigs than simply having chops.