Check out neighborhoodscout.com for a basic understanding of the neighborhoods also check out rentometer.com for a very basic estimation of rents also. 

Notes: The house has a base price of ~$350k.  

I have a basement in my primary home that's been rented for 8 years.

I need to establish a base value for a property that was deeded to me by my father that I sold. 

Plus you could become an agent for USAA and assist military members if there is a base nearby.  

We are currently looking to buy a house with a basement suite to help out with the mortgage.

Besides giving you actual sold comps (I know the data is correct as I had my realtor pull the same comps for me a few times and everything was spot on) they have capabilities of a basic CRM, skip tracing, and you can build marketing campaigns including direct mail (you can design the mailings, order them through the website to be printed and mailed for you) and ringless voice mail which you can record and manage right there as well. 

We are about to sell our second rental and I am interested in having a primary home with a basement apartment and having a detached garage with another apartment over it.

I'd like to either buy a home with a basement apartment I can rent out or a duplex, triplex, our fourplex if possible.

I'm leaning towards building a basic spreadsheet to track this info and thought I should see if there are any good examples out there before I re-invent the wheel.Thanks for the ideas.