My goal is to focus on the investor niche and not the retail market. 

Ask if they know anything coming up for sale.You might consider Niche or Specialized Housing like student housing.

And about talking about the comparison I was kinda just talking about niche markets.

Theres all these different ways to find "motivated sellers", but most of them are not worth putting your time in because theres too few sellers to be found, so therefore youre scattered trying 20 different niches.

In closing, I'm not "blasting into the forums with contrary statements of others that have expertise in this area," if anything, you're doing the same thing to the Rent to Own aka Lease Option aka Lease Purchase niche.

I couldn't agree with @Amit M. more about the variable rate financing aspect, along with the differences in vacancy, especially if you have a single-tenant building, large single space, or unique building.

I’ve heard that NPNs can be very lucrative, and I hope to experience that first hand, but what I’m not clear on is the appropriate niche strategy for myself.

I admittedly have a distinct bias against wholesaling, so I would first suggest if you do go that route you do a lot of advance homework and due diligence before embarking on that niche.  

Scott The Book on Flipping Houses, The Book on Estimating ReHab Costs http://www.biggerpockets.com/flippingbookGood read The Real Estate Agent’s Ultimate Guide to Working with Investors http://www.biggerpockets.com/renewsblog/2013/08/24/real-estate-agents-working-with-investors/You might consider Niche or Specialized Housing like student housing.

To take it a step farther, you could pursue a relationship with your local housing related non-profits and perhaps develop a niche for serving low income renters with a constant stream of referrals from the agencies, and usually some financial backing from their rapid rehousing programs or similar aids.