I just texted my son to see if they had any openings in their apartment this summer and he says they are all staying. They just can't bear to leave beautiful Iowa City, I guess. I'd think the best way would be word of mouth, just have him ask around. I've known kids in our college town who have found places for $100 a month but they can afford to wait until the last minute because they live here anyway so worst case scenario would be living with their parents. Both my kids have stayed in their apartments over the summers since they have to pay for them anyway.
Off topic, do you know if they can get in-state tuition at Kirkwood CC if they have an apartment address?