But to be honest - most cars in that price range will have already been destroyed by Polish roads and not worth the hassle. Certainly, anything under 5000PLN is likely to be a bit of a wreck - and it's not easy to find a good second-hand car in Poland.
I totally agree with delphiandomine. Most cars in that price range will probably be death traps in all honesty. I would consider the rent option as in the end it could prove to be cheaper!