There is a subway, an AT&T store, a hair salon, the owners business, and one vacant unit they are working to lease for a nail salon.

Find out what areas are good to invest in, that can collect the most rent and the crime rate for different areas. look for convenience, sub-way, bus, train, schools, even hospitals ( some people like to live close plus you may get Dr's and Nurses). here is a link that can help if you haven't gone to it yet: http://www.biggerpockets.com/renewsblog/2014/12/26/demographicstelling-real-estate-indicator-analyze-investing/

Do you want to be by a specific subway?

We have abundant, cheap land not found in other big cites and metropolitan areas.And although we are really bad at Mass and Rapid Transit (no passenger trains or subways) we are really good at building roads and highways that keep everyone moving and the area expanding.

Also, I would avoid a single fam on the same block as subsidized housing but generally speaking, in Boston, buyers and renters are used to dealing with parking issues, neighborhood diversity and train/subway tracks.

For full out renovations I use name brand valve sets with replacable valve stems, enameled cast iron tubs from HD, and white subway tile with detail accents for a classic looking reasonably priced tile job.

I listen to REI podcasts a lot since I have a lot of time on my hands on my daily subway commute.

Its a long game though.. and in many instances if its just cash flow you want.. real estate is not always the best thing anyway you may be better plunking down 100 to 200k and buying some subway sandwich franchises make you far more cash flow than any rentals. 

Also, I'm aiming for big streets, or transportation hubs (subway station, train stops, etc).

The major benefit being the access to the Broad street subway.