My advice is to rent for a month or so by Airbnb while you search for an apartment with the help of an OLDER experienced Polish colleague. Having a Pole help you find and apartment and do the talking will save you a great deal of time and trouble. They also know what to look for in terms of location and the condition of the apartment. For example, an apartment may seem cheap, but located in such a way that you will require an inconvenient commute. Standing at cold tram or bus stations during the winter can sap your energy even before you get to work.
The other two biggies are the kitchen and the windows. A lot of Polish apartments have a kitchen that is so small that it is near impossible to use for everyday cooking (they are called "kitchen annexes"). You're going to find that you will be cooking at home less and less and eating out more and more, which is going to cost you.
As for windows, this is why you need and OLDER experienced person. A lot of Polish apartments have windows that were improperly installed. Slipshod work was the rule rather than the exception during the 1990s, when most Polish apartments were refitted with new windows. The problem is not only are the rooms cold in winter, but cold air can enter through the gaps and dramatically increase your heating bill.
Make sure your apartment has a washing machine, because laundromats (laundrettes) are practically non-existent in Poland, and those that exist are very expensive.
Walking distance to the grocery store is also a great plus and timesaver, You wont have to schlepp bags all over the city, and you can just pop down and get any ingredients you forgot to buy while you are cooking.
And don't forget to fairly compensate your colleague for their time and trouble. They are saving you a heap of cash.