-Large plastic tote: $12.99
-Economy bathroom exhaust fan (50 cfm): $22.29
-3" x 10' flexible ducting: $3.49
-Plastic clamps for 3" ducting: $1.39
-3M fiberglass filters (16 x 20", three): $4.39 (enough for at least 10 paint jobs)
-4.5m extension cord (2 prong): $5.39
The basic construction process (sorry for not taking pics of the build, but it's pretty self-explanatory). Use your common sense please, I can't take responsibility for your actions or mistakes.

1. Partly disassemble the fan so that you can route the 2 electrical wires outside. The inside has a 2-prong connector that you plug into the fan housing.
2. Place fan on top of plastic tote, mark the perimeter with a Sharpie.
3. I had some foam tape that was 1/4" thick, I stuck that where the fan housing would meet the tote, to make it somewhat air-tight.
4. Cut a hole within the perimeter line, at least an inch or so inside the perimeter, for strength to support the fan. It's not really heavy anyway, it's just what I did.
5. Find 3 pieces of L-angles, drill a hole at each end and find some screws, nuts & washers to fit. I didn't even have to drill my particular fan housing, holes already existed.
6. Bolt L-angles to the housing. Place back on tote, mark the mounting locations of the remaining 3 holes with a Sharpie. Drill holes where marked.
7. Bolt the fan housing to the tote. I used washers on either side, inside the bolt-heads & nuts, to again help with structural integrity.
8. Attach the duct to the fan's exhaust port with a plastic clamp.
9. Cut end off cheap extension cord, strip a half-inch off each of the 2 wires.
10. Solder these 2 wires to the wires routed through the fan housing in Step 1. Make sure to shrink-wrap the exposed wires, you're talkin' 110V alternating current. Unlike milk, it does NOT do a body good.

11. Cut off a section of furnace filter to more than cover the hole cut out of the plastic tote. I attached it with Velcro at the corners, for easy replacement. I attached the filter section to the underside of the inside of the tote.
12. Plug in cord; fan exhausts through the duct.

I might get a chance to try it out tonight, but it works great. The only variable is the filtration. I'll see how it works with furnace filter material. I'm not trying to filter out fumes or gases, just prevent overspray and keep dust off the painting area. Wear a mask if fumes concern you. Don't place the paint booth or paint anywhere there could be sparks or fire, the fumes can be flammable. Again, use your common sense.