Here is the quick and dirty about various chapter houses at Iowa State. I would say there are more chapters who had their houses built for them (most are anywhere from 40-90 years old) than those who remodeled regular houses, but there are a few of those as well.
Kappa: The house was purchased from the Baptist church up the street in 1947 -- it used to be their Student Ministry -- and then an addition was built in 1982. For a while there was a rumor floating around it was once a funeral home, but we could never verify that. Supposedly, we are haunted by Annie, a michevious but harmless ghost. At one time in the late '40s, Kappa purchased the lot where TKE now is and even had house plans drawn up. We're all glad we stayed where we are, though, because not only are we the closest house to campus, we're also the closest to Campustown.
Phi Delta Theta: Their original house was on Welch Ave. across from Pi Kappa Phi. It was in disrepair and they moved into the former Alpha Phi house (which was a church before that) during my sophomore year.
Alpha Sigma Phi: Took over and extensively renovated the former Sigma Nu house. Previously they were located on Lynn Ave. in the former ZTA house (which is now apartments, I believe).
Acacia: They sold their house to a Bed and Breakfast operation when they left campus. They recolonized in 2000 and were able to purchase it back.
The former
Phi Kappa Tau (located right between FarmHouse and Kappa Sigma in Greekland) house was bought out in the late '90s and turned into apartments.
I don't know if
Sigma Pi has ever owned their own chapter house. They lived in Pi Kappa Alpha's old house while they were gone. When Pikes came back to campus, Sigma Pis moved into the Phi Kappa Psi house. When Phi Psi came back, I *think* Sigma Pi moved into Delta Sigma Phi's house (but I'm not positive). If/when Delta Sigs come back, Simga Pi will be out of a house again.
The old
Alpha Xi Delta house is now a women's shelter.
When I was on Panhellenic Executive, I found an old Rush booklet from the mid '60s that contained a great hand-drawn map of all the Greek houses. It's so funny to look back and see what chapters used to be on campus and where they were located.