For the record, I lived in Danville (15 miles south of Walnut Creek) until 11/08. Lived in a very nice condo association. Fees went from 197 in 2000 to over 400 in 2008...and there was talk of a 15K to 20K assessment for roofing. At that point the assessments were just getting to be too much to justify.
I know agents in the area who can help you crunch numbers to see which property or type can make the most sense for you. I have run numbers for areas in San Diego County (where I now live) and investment property in the 400 to 450 range will easily have a positive cash flow on a rental basis. I think it would be much the same in Contra Costa County.
This is like a "baby-boom" for Landlords.
Figure that these people probably do not want to move from a 4 bedroom, 2500 sqft house to a 2 bedroom Condo.
My suggestion would be to look for 3 & 4 bedroom houses and not in crummy neighborhoods.
This is probably a good target client/tenant.
Good luck and may God bless
Unfortunately you are about 10 years too late. In today's environment many HOA's have put in place rental restrictions that the banks and laws now support. With the glut of investors picking up condo's in the bubble era many associations have lists of people wanting to turn their properties into rentals.