They were using a new snow removal company that was unaware of property lines in the neighborhood.

Also, what are some good resources I should be using as a prospective investor in this market - people I should talk to, groups I should join, publications I should read? 

Also, we plan on using a first time home owners mortgage with a cosign from my parents.

I'm guessing you will be using a different lender and contractor on this one?

If we'd have to get a commercial loan using an LLC, what other options are there to share equity while using a residential loan?  

I once had a tenant call at 10:00 pm on a Sunday night complaining about lack of power in a bedroom he was using as a study. 

Then you need to pay close attention to some other large ticket items that may be needed like rough framing - adding or moving walls, beams, posts, etc (as well as the rough framing costs to change the size of doors, windows, etc), insulation, and foundation.If you were ever told by some guru or rookie that you should or they estimate rehab costs by using a price per square foot, run for the hills, they have no idea what they are talking about as that is the worst way possible you can accurately estimate rehab costs!!!

Currently we are using a Home Depot Commercial Revolving Charge card for the majority of our purchases.  

You will get your first deal with this tactic using a listed deal on the MLS such as Possible Short Sales, Probates, Etc.... or off market properties from places such as Zillow. 

I've been using a basic excel sheet but have had issues with excel on my Mac.