OK. be aware that he is selling it at $6.95/ft and you would need 8' to make a 16:9 screen. That's approx $50. You would be looking at a about 100" screen at most.
You would then need to add lumber. Figure about 35-40 ft of kiln dried 1x4 pine or preferably poplar. Also some scrap plywood for corner bracing. Figure $30-50.
You then need grommets and bungees to tension it. Another $20
Once you get it up, you will discover that you really want black velvet for the edges. Another $20+
So, you are in for $140ish for a very basic screen using this material. One of the things you pay for in the commercial screen is a sturdy frame and a good tensioning system. The vinyl sheet is difficult to get wrinkle free. In comparison, I bought my 120" Elite Sableframe for around $320. You should be able to get a 110" for around $300.
There are a number of other choices in that approximate price range. WilsonArt Designer White laminate is a popular choice. So is painted masonite. There are various paint mixes floating around. DFergie has had good luck with spandex fabric over laminate. There is also blackout cloth which costs about the same as the vinyl material, but is easier to tension. These are all good choices, but probably won't save much money once you start trying to make it right.
Perhaps the least expensive is to sand your wall smooth and apply something like the silverfire paint mix that MississippiMan has over at AVS Forum. You can put that up for around $60 including the velvet frame and a weekend of sanding and painting.
Lots of good reasons to DIY a screen, but saving money probably isn't one of them in the long run.
