Backpackers like nice expensive tightly cut gear all fancy and new, but its not required to have shiny new gear. Many homeless people who live in tents, separate the inner tent from the outer tent anyway. That is - they choose the space and area desired and get an inner tent that does that [ its much cheaper than a whole tent], then they cover the tent with several layers of blankets for insulation and finally cover it with a tarp or more often, multipe tarps.

I have a REI screen tent that I got from one of my homeless friends for $10. It has a nice intact inner tent and a torn cover that smells like a cat used it... It'll probably be thrown away. Anyway I have an ultralight silnylon tarp that I can pitch over the inner tent making a useful and flexible combination thats bugproof, light, and has some wind blocking ability.
Jim