You can simply slope it at a 2:1 slope, horizontal distance from top to bottom is twice vertical height, and grass it, it will be stable. 

Retired so no W2s.

The property is in a nice, stable part of Milwaukee, and the numbers work quite well for me.

Also, for reference, I work full time W2, and am able to put back around 40% of my paycheck each month into savings after retirement/taxes etc. 

Is a $10M total on our retirement account balances an obtainable goal for a savvy investor with the ability to choose to participate in great deals?

Very desirable, but largely already mostly discovered, would be hard to find a deal.Park Slope- Probably the most blue chip neighborhood in Brooklyn, incredibly stable, will most likely continue to appreciate at a modest rate. 

We love the Santa Rosa Beach area (we have a small property there that was supposed to be a retirement home..now trying to decide what to do with it!)

I am a disabled veteran and a retired nurse of 20 years.

Some are individual, LLCs, retirement accounts, money market accounts, etc.

Rather, the plan is acquiring real estate as a means to diversify the plan's holdings and better protect and grow your tax-sheltered retirement savings.