You can also use online real estate listings for areas you're not thoroughly familiar with. I've used Zillow and Realtor.com to look inside the Manhattan townhomes that are one-room wide.

I also agree with Google Maps which also has Street View and possibly reviews with photos. What kind of 'downtown' is there? What stores are there? What's the train or bus station look like?

If it's a more fictional setting, perhaps tvtropes.org?

Sharon from New Jersey