Medical cleaning is definitely different that residential and even other commercial cleaning.
Tickle is correct there are many things required that are more stringent than commercial cleaning;
Proper P. P. E. (Proper Protective equipment)
Universal Precautions. (Safety for you, your workers, the client and the patients.)
Proper Cleaning solutions for stringent cleaning to kill germs and infections.
Removal of infectious waste. (Red Bags; proper handling, proper disposal to a designated area for removal by others...)
Are there exam rooms where any surgeries are being preformed? If so, then a strong disinfectant will be necessary.
Places like the exam rooms will have to be cleaned very well....each night everything from eye level down has to be cleaned well. Once per month those places above eye level.
In my business, 6,000 sq ft is not necessarily a large building. However since it is medical there will be special requirements and will take more time to clean properly.
Pricing varies all over the country and now with the economy they are starting to come down (not good for us I am afraid). In the Chicago suburbs a medical building like the one you described should competitively bill out monthly at a high of around $1,260.00 to a low of $$1,020.00. This is only my suggestion.
Now, you are the one that is responsible to make sure that the amount you choose works for you, again THAT is your responsibility, not mine. I can tell you that normally an average medical center can be cleaned at a rate between 1,890 to 2200 sq ft per HOUR, a lot depends on the density of equipment and furniture.
That is an average of approximately 2050 sq ft being cleaned each hour and that (based upon your 6,000 sq ft figure) would total be about 3 hours each night, 18 hours per week or 78 labor hours per month. Add that to the hourly rate, include all your overhead, profit, supplies, insurance, etc and you should have a pretty good idea of what you might quote/charge.
I hope that I was helpful, please respond so that I will know.