Cleaning can be hard work but you can also make good money because not everyone is willing to do this kind of work. To make even more money you can develop a specialty such as cleaning offices, industrial sites or even hazardous waste removal.
In its simplest form, you can start a house cleaning business with a single client. Most customers will want their home cleaned regularly so this is another good repeat customer, steady income business. You can charge by the hour but most house cleaners charge by the job. That way both you and the customer know exactly what the charge will be in advance.
Most people first grow their house cleaning business by adding a couple helpers to work alongside them. This way, they can keep a close eye on the quality of the work and remain the primary contact with the customer. You can of course grow this business much more quickly by adding additional crews. Many entrepreneurs have built their cleaning businesses into multi-million dollar enterprises.
Another possibility is office cleaning. One of my friends built a highly successful solo business cleaning the offices of small businesses at night. These businesses trusted him with access to their offices so they were willing to pay him good money. He only worked 4 or 5 hours each night and still made an excellent full time living.