A common misconception when it comes to poor people is that rags are cheap. On the contrary, basic 'wiping' needs are not met with out a significant cost, an estimated $5.00 a month, which adds up significantly over the coarse of a lifetime.
Most poor people have taken the obvious fool-proof approach of taking paper products in the form of toilet paper, paper towels, and tiny restaurant napkins from public places, but there is another way.
Use a regular sports sock as a dish rag, a Kleenex, a washcloth, or a small guest towel, then simply wash it and use it as a sock again. Sport socks can also double as a padded case for expensive electronics that you most likely don't have, a coin sack for ground pennies, and a glasses case.