Tell your professor you want to change the topic to specific case studies of specific but randomly selected streets in different areas of the county, get the info from the county recorders office (free in person, 1600 pacific coast highway, 1st floor, last time I visited). Just do one street at random, then another in a different town but stay within the county so you can get it in person.

The census data is crap, asking the association of realtors is like asking the pope how many child molesting priests are in the church. You need to pay any of the data outfits and they won’t have what you are looking for, do a news search and see if some reporter already wrote something similar. Yahoo neigborhoods will do it by zip code, not sure if it goes back far enough and where that data comes from is suspect. As far as average mortgage payment, I don’t think that data is harvested, in person title search of each house will give you a peek at some of the loan docs and you can see the helocs. With all the 80/20’s out there and helocs, you need to look under the covers to get the real story.

Average sales price is another lie, incentives aren’t reflected and they can be 20% today but were non existent in 2003. I am not trying to criticize your project but if you were an author and gave me the numbers you are looking for in an article I would dismiss it and could make you crawl into a fetal position on the floor in a debate if you used those numbers and cited those sources. This is akin to telling me the average weight of a Californian based on info culled from driver’s licenses, bad questions and self reported information will only give a reader and an analyst an incorrect view. The packers have a better record than the chargers but the chargers are favored on the road, why? because an in depth analysis of the variables sheds light on the truth. If your project is to get a master’s degree, nut up and go get the real story. If you are doing an article for your high school paper, just say that fraudulent lenders screwed the uninformed and interview a family facing foreclosure, no strike that, the San Diego Union already does that.