Do not know anything about Krakow student market but here is food for thought:
Krakow has 183,000 students and property costs on average 6,275 per m2; Poznan has 127,000 students and property costs 4,098 per m2. So while Krakow has 44% more students than Poznan, property is 53% more expensive in Krakow tham Poznan. Therefore, don't put all your Polish eggs in one basket; check out other cities as well when you visit in the spring.
Of course I have a vested interest in Poznan but the stats are valid.