As with any country, in the building trade there are cowboys and there are genuine companies. Here are a few ways to know the difference

Half Fitting
This is the practice of producing a quote that appears to include everything but cheaper than most other companies. The result is usually that the bathroom wall tiling is very low, the wood or tiled flooring does not have edging, the walls are only painted once and look patchy, the kitchen is a cheap off the shelf product from a DIY store, and so on. This will leave you with an apartment that views poorly. Note also low tiling in the bathroom can allow water to seep between the wall and the tiles causing them to come loose.
Double check your quote, what will they actually do?

Cheap Products
There are some incredibly cheap materials available on the market - tiles from 20 PLN/sqm, laminate from 15 PLN/sqm, and so on. But if you want your property to last well on the rental market or sell for a premium to the ever-savvy Poles this is a false economy.
Check the brands used by the fit out company are well known on the Polish market.

Hidden Extras
Some companies quote for the basics but then come back during the project demanding extra funds for items such as door handles, floor edging and numerous other materials that "were not included in the original quote and we thought you knew that".
Ask the company to guarantee the price before works start to avoid this.

Cash in Hand
At first this is a tempting option. You save money because you don't pay the VAT (up to 22%) but there are three problems. Firstly if there are any issues with the fit out the fitter can deny they ever did the work and there is no paper trail to prove that they did. Secondly you cannot offset the cost of the fit out against your rental or resale income if you do not have a proper VAT receipt. Thirdly it is illegal and if Polish Inland Revenue ever catches up with the fitter, they may catch up with you as well.
Check you will get a VAT receipt (Faktura)

"I can do it cheaper"
Most often the words of an inexperienced person or someone "between jobs". They will carry out substandard work and then, when you complain, say "but it was cheap!".
If a person or company offers to do work that is cheaper than anyone else it is too good to be true!

And there's more > > > >