I have started a construction cleanup company and I want to know how do I estimate? Is it by the spuare feet or by the hour

It is not a good idea to post your new question as a answer to someone else's question, you are not likely to get a lot of answers that away.

This is a hard issue as there are a lot of various difference types of clean up.
Every area will also have issues as to cost of disposal.

Often you will need to talk with some contractors and find out what is the going rate for the area.