I guess that I have generalized the whole rental market in the c

During 2008 housing crisis, the impact is very localized.  Some areas are hit harder than the others.  There are a lot of reasons for that, demographic, type of industries, race, etc.  I can see that your area's real estate market is very volatile.  I live in midwest.  My local real estate market dropped about 5 to 10% during the crisis.  My rental income did not go down at all.