When you don't have a garage or a barn where you can saw and paint you are forced to be creative in creating an isolated area for that purpose. I have made such an place and would like to share it so maybe you will find it useful.
The idea appeared to me when I was planning to start building an arcade machine. I needed an area that will keep all the sawdust and spray paint inside without contaminating the surroundings. On the attic I have my computer and a electronic workbench so sawing and spraying with paint is not a good idea. Luckily I had a small corner that I could separate. There was a desk and some boxes, so I started by cleaning up the area. Unfortunately this area is quite low, so I can not stand there and have to do everything on the floor.
I have bought some plastic drop cloth and started to make the separations. I used a stapling machine.
After a short while I was done. I have also covered the walls inside, so they will not get any paint. For the floor I have used a black plastic drop cloth.
This is how it looks from the outside.
The only thing that I need to add is some kind of ventilation, because it does get very muggy inside. Wearing a dust mask and eye protection is also advisable.