My plan is to buy a place in the range of $200-280K with a walkout basement so I can rent it while we are living upstairs.

Homes in the neighborhood range from 500 -1.25 mil.

If you need rehab and a stabilization period, you may see rates creep up into the mid 5% range. 

I would probably stick with growing your portfolio with mid-range cash flowing rentals (focus on low maintenance properties), or scale up into multifamily units (if the numbers make sense).

What i found interested me the most was Multi-Family in the 5+ unit range, the relative safety is what initially attracted me to it and as I learned more about it it became my passion.

If you have personal assets in the 900k+ range, I think it'd be a mistake not to have coverage. 

You're absolutely correct that you can just as easily go to any site and filter through a list of properties in your desired area and price range but I believe their value comes into play more when it comes to details that might not be readily available to everyone. 

The other fourplex was listed at 980 a month so all right in that range. 

How should we adjust for finished basement sqft with respect to coming up with the range of $/sqft that a neighborhood can support?

As far as foundation you will get a HUGE range on prices to fix, from different contractors.