A bit puzzled by this........................there is a huge difference, between 10 and 20 of anything !
I do end of let cleans, for about 60 properties, but this only results in a very low volume of work and it's very much at the lower end of the pricing scale.
The machines you mention, are really just very low powered, tiny capacity machines which are really only capable of very small jobs
There's a regular supply of suitable machines crop up on here