Hi Jones,
Tips on what you are looking for would be difficult to advise. Each client is different and you have to judge each situation on its own merits.
If you want tips on just saving money you may not actually get the result that the client is actualy looking for. Just because the is a different product on the market that can save you 50% or more does not mean it would actually give the same or better result.
You need to find out exactly what the client wants to achieve apart from "clean" and high standards.
The type of offices and the actual state of the building will depend on the advice you can give. If the building is clean and the toilets are clean and fresh before you start then you wont need to purchase high cleaning products as all that would be required is a gentle wipe over to maintain the feel and look of the results already in place.
If you are cleaning a factory where the is grease, or a Quarry where there is nothing but mud and grease combined then you need to advise on certain chemicals to remove the debris and bring back the original look of the floor.
What is your clients objective in the way of the environment. Does he only want Green chemicals. These will be more expensive.
Window cleaning, depending on the condition of the building and window structure, UPVC, WOOD etc would you advise using WFP with 000 TDS reading or simply use traditional methods such as a sqegee and mop.
What about 2005 hight regulations.
Coshh sheets, method statements, Risk assesments.
So for me to advise I would need a little more information. As we could or I could advise incorrectly.
Best of luck Dave