Where could I download Income data at the Block Group level, actually I'm not sure where or how to download it at the tract level either. I would be interested in the most recent data that is available.
You can get this from the US Census Bureau website, Here.
Try the 2007-2011 Block Group data, but it's in geodatabase format. you can also try the 2010 profiles there, which are listed in census tract as well. You may need to clip them down to the area of interest, but they conveniently come ready made for analysis. Otherwise, you will need to use the American Factfinder part of the US Census Bureau to create tables you want. By doing that you should be able to get 2013 estimates for your area of interest, but you will also need to download their corresponding shapefiles from the TIGER site. Keep in mind, you will need to join your American Factfinder tables to your TIGER line files in GIS, and sometimes the fields you will use for joining will be in different data types. For example the census track ID in one table might be in string while in the TIGER file be a number...so make sure to check that if you're going about it that way. Good luck!