Having just spoken to pretty much every bank on the market, they'll be looking at:
a) proof of continued employment for at least a year
b) average income of earnings over the last six months
and those were the most liberal criteria. Other banks took longer periods to calculate their average, or discounted employment periods of less than two years. However, I have no idea if they'll take into account overseas earnings. If you step off the plane and into a bank, they'll not have anything with which to measure your credit worthiness, and will have to reject you on the spot.
On the other side, most banks only require a 10% deposit, with a few requiring 20%. Citibank openly state on their website "Polish Citizenship Required" so they've obviously had their fingers burnt by overseas investors in the past, so it's worth talking to a mortgage professional now to find out what paperwork they'll want from you in order to grant a mortgage.
Related: Need a bank for property purchase in Krakow
What is the best bank for foreigners buying property in Krakow?
Thank you for asking this question grspring.
After much research on the internet I saw how beautiful Poland is, and I would also like to know if foreigners can buy property in Poland. If it is allowed, which one is the best bank to approach?
Any replies would be greatly appreciated.