A number of years ago, I wandered over to the local electronics wholesaler and picked up a 6" fan and some cabling and switches. This went into a piece of 1/4" plywood designed to just fit in the window in the back room when the lower sash is raised. Cost was probably about $30.
This eliminated the smell of VOCs when I painted but did nothing for dust. So I cleaned up the area, which I should have been doing regularly anyway, and assembled an improvised booth as follows:
One 89 litre Rubbermaid storage box, made of 0.080" flexible semi-clear plastic, $19.97
One 4" dryer vent connector, $9.42
Two 4" hose clamps, $3.94
One package, 4' dryer hose, 20' long (anybody want 17' of dryer hose?), $15.55
One package, LED strip lighting, $39.98 (I am sure there are cheaper options)
One package of 4 plastic shoe boxes to hold paint cans, $3.97
Now I just need a transition piece to go from the 4" dryer hose to the 6" fan. I sense some duct tape in my future ...
Total with tax, including the fan but excluding the strip lighting, about $100. The plastic can easily be wiped down with a damp rag, and the size is about right. It even has a lid that can be used to control airflow into the box. The dryer hose and lighting can be quickly disconnected so the box can be moved. And the strip lighting comes with a remote control allowing you to pick different colour lighting: red, blue, green, etc. Mood lighting in the paint booth ... the only issue might be that the white is not really yellow enough to mimic daylight, and it may be difficult to judge colours in there. Stay tuned.
Update: The hardware store had a 6" to 4" reducer, three little angle brackets, and a box of #8 x 3/4" machine screws. Now I just need to paint something ...