I can tell you as a busienss owner and resident of an office complex that positng flyers opn cars will most likely get you kicked off site and you risk pissing off the peopel you want as clients BUT here is a good way to handle it that WILL work:
take the time to visit each business in the complex and speak with either the receptionist or HR manager (chances are you will deal with the receptionist) Keep in mind that she is the true gatekeep of this office and she knows everyones perosnl habits better then you think. Explain to her what you offer and why it is beneficial (and treat her with respect) and ask her if she knows of anyone in the office that might be interested keeping in mind she probabaly knows the people in the office that have an autotopian mentality and will hand carry your flyer to them and or post it on the b-board...If you want to, take it one step further and hire her...tell her she gets you x cars to detail and she gets hers washed for free (she doesnt make a ton of money and her car is most likely filthy so she will love you for it)...case in point, I called a detailer that I found tru this site to come and do my boat, he was smart and knew it would take 3 hours to do it and he called back told my receptionist that he would be there on Tuesdat at 7AM and to please ask of anyone needed a hand car wash and interiro clean for $20.00...he picked up my boat at $150.00 plus 4 other cars at $20.00 ea plus tips
as for power and water...I have it here and dont care if you use it but many places do not so a small genny might be good and some qew?
Hope this helped