But each extra body = more trash, more towels, more sheets, more dishes, more cleaning, more wear and tear, more potential damage, Etc...In one of our places, we actually converted 2 of our 4 bedrooms into a yoga room and office respectively, to cut down on the number of potential guests and problems.

If we buy a house that’s already been used as STR are we able to  immediately rent it (post cleaning and furniture set up ) without this permit process .

The outcome is going to be a great rental property where the market rent is $1350 for a good clean 3 bed.

Apartments are "easier" than SF homes from a maintenance standpoint (no grass to cut, gutters to clean, etc.)  

However, if there are other liens on the property then you would be responsible for paying them too (if you wanted a clean title).

Is there a way to contact real estate agencies or homeowners in order to offer our window cleaning services?

I called a window guy I use and he basically dismantled the entire louver mechanism that controls the shutters themselves and then cleaned them as well as each shutter joint.

Or do I need to dig deep into the legal side of it first and really understand that?

@James Wise he was clean for many years and going to my church, but that was five years ago.

Hard to find deals right now.I personally would not consider cleaning my own STR's.