There are a lot of opinions on how much to charge and a lot of that depends on the market in your area. I suggest cleaning your own home 3 times and time yourself doing it. Don't bother with laundry and dishes, etc. Just focus on cleaning tasks you would handle for someone else, like vacuuming, cleaning bathrooms, windows and so on.
If it takes me 2 hours to clean my 3 bedroom 2 Bath home at 1200 square ft and I want to make $30 an hour, than I know how much to charge a house of comparable size for the same services I just did.
Obviously commercial cleaning is a bit different, but the same principle can be applied to window cleaning, carpet cleaning, pressure washing, etc. Start with friends and relatives, get a checklist or work flow together and THEN start offering your services.
This will give you the BEST idea of how much money you can make long term. 4 homes a day @ 2hrs each (x) $30hr (+) 1 hr of drive time = $240 a day (as an example). You would still need to add supplies, insurance, vehicle expenses, etc.