You can try to find the opinion itself, but I read the reasoning as being that: (1) such murders have nothing to do with the physical safety of the house; and (2) requiring sellers to disclose such facts may lead to sellers having to disclose other "stigmas." 

Learn what the different factors that could make a deal good or bad (there are physical properties of the house as well as some more difficult to quantify properties) There are plenty of resources here on BP that will help you learn to do that as well as many books that will get you jump started (I would recommend starting with Millionaire Real Estate Investor).

Is that tax deduction less than your physical loss in revenue?

Even with a property that only has 5% physical vacancy, you should account for bad debt, loss to lease, etc.

Typically based of historical figures with adjustments made and explanations as to why you think you'll be able to increase rent & decrease expenses.When speaking with the property manager ask the following to get started:what other properties do they manage:how does this property compare - physically and financially (rents, expense ratio, etc.)What is the going cap rate in the area, what are they basing their asking price off of? 

My husband would love to work his way (after he pays his "dues") from being the one physically doing all the work but instead being the one who manages the project (while of course still doing some of the work).

PS Bonus points for ability to generate 3-day notices from the software, and ability to dispatch physical letters without manually print/fold/stuff/stamp/mail  (ala mailaletter, click2mail)

I'm a bit concerned about anonymity, but I was told that they might require an actual physical address.2. 

I realize now that I have a decent amount of equity at my disposal and I'd really like to use it to grow our little side thing into a full-fledged business.It is a challenge to be actively involved when I'm not physically present, but I'm fortunate enough to have a reliable partner and property manager that handles nearly everything.

That and no capital are the ONLY two things preventing me from physically acting.