So I'm cleaning a residential home and finding out that all the window ledges in the back of the home in the basement are caked with mud. Scraping mud out obviously takes more time and more effort than what is routinely to just clean them so I'd like to charge extra for this work.

Have you found it's better to let them know right then and there what the charge is or do you add it into the invoice at the end or do you not charge anything extra?

There and then
was it not noticeable when you went to look at the property before pricing

I'd prefer to let them know immediately but I let them know even at the beginning that something like that might happen, it gives you a good reputation and they will most of the time agree

Yup right there is the best choice for me because it would feel like scamming them so the reputation would drop, I do value my customers as people too so I'd rather to that than disrespect them