Here in Uruguay* we have a reasonably good solution, it's a "flat tax" (currently U$ 50/month) that includes healthcare as a benefit, which makes it very useful for a one-man business - for example, most window cleaners, car parkers and other "almost-beggars" pay this tax (the maximum income for the business is U$ 25.000 gross yearly).

It's called "Monotributo", if you speak Spanish look it up.

(*I believe the same works in Argentina)