Out of the three Solano County cities you mentioned - Vallejo, Fairfield, or Benicia - my gut feel is that Vallejo will cash flow best. but a a cost due to the challenges of crime & the economy there.In general, the safest & nicest area of Vallejo is known as "Glen Cove" - if you look at google map, it is bordered on the North by 780, on the West by 80, on the East by Benicia State Park, and on the South by the Carquinez Strait.

The laws in each state about real estate vary from state to state, each state has the right to control how contract and land law works inside its borders.

The numbered streets run east/west and are numbered south to north (2nd St or Patterson Plank is the southernmost street/borders Jersey City, 49th is the northernmost border with West New York), John F Kennedy is the westernmost border with North Bergen, and Palisade or Park is the easternmost with Weehawken or Hoboken. 

Once time my Dad and hise wife were pulled out of the car at the border art gun point because they had cruised across for a few hours for luch and on the way back they both answered their professions were "Real Estate" and the border patrol didnt buy it. haha Thats the issue, how can you describe exactlly what you do in ONE word! 

Simply looking at the city's borders, sure.... but the Cincinnati MSA is larger than Columbus.... also something to note, most of Cincinnati's growing neighborhoods are to the north(mason/liberty areas), which is just south of Dayton....

Part of my construction crew lives near the border so getting up there isn't too challenging for us, but the traffic that @Mike Nuss called out is no joke for most Portlanders. 

I would like to point out that NC real estate is quite high right now, but just over the border in Southwest Virginia can be incredibly affordable by comparison.

@Hannah Canario  I have a property in North Bergen as well close to the Jersey City border and I've been able to find good tenants through the sites mentioned above.

But Like I said, this is not legal/tax advice and you should consult with a cross border specialist before making any move.  

I think 5 is probably the correct number to have.With everyone else that having Boston and Cambridge as different sub sections makes no sense since they border each other.