Making envelopes for cash does sound pretty sucky. My single parent mum's only paid job during my lifetime was delivering newspapers, so I can empathise on the crappy pay for work front.
Thinking about this more the only thing I actually want
made any time soon, is a solar cooker in order to be able to cook food for free when I’m homeless and living in a tent this summer. It’s something I want to build myself soon as it’ll be cheaper and the skills could be useful to learn. I don't know if it's suitable but I thought I’d throw the idea in there as a different sort of possibility. I know very little of what life is like in Vietnam, but the overall picture everywhere in the future is pretty much certain to be rising fuel/energy costs and worsening economic times.
It was one of Archdruid Greer’s blogposts where I first heard about solar cookers – link
here (relevant bits several paragraphs down). He seems to suggest there could be a business opportunity for someone making and selling them. His blog and the related forum is generally good for tips and inspiration on low-tech DIY / energy saving / handi-craft.