Generally, cleaning jobs on which to bid aren't listed online. In order for a person to actually make a fair bid, they need to be able to sell what they have to offer to the potential customer and see, in person what any particular job might entail as far as the work that needs to be done. You might communicate with a potential customer via Internet communication of some sort, but that would be after initially meeting with them in person.
What kind of cleaning service do you have and how long have you been doing it in order to make a profit for yourself, please?
Yes, people can post all over the place online on many sites for what they can do for people. It doesn't have to cost the person advertising anything at all, other than time, in order to do that.