Rentals in Morgan Hill are doing ok right now. However, 2b/2b type units tend to be less desirable than other configurations. Also, the location is going to make a difference - in some cases, a big one.
I am including a web link to my search engine. You can search for rentals there. Just zoom in to the area where the duplex is located and see what other properties with the same features are offering.
In general, rental rates have risen during the foreclosure situation. The key is to get your math right before you even buy the investment property.
Hope that helps,
Whitelaw & Sons Real Estate Services
Morgan HIll, CA
As for duplex there was only 1 traded hands last 12 months fetched around 400s(bank owned). Duplex does not come on the market often here in MH.