Plus they have a whole suite of features that are essential for landlords. 

What resources or tools are essential for conducting thorough market research?

If the property appraises at $500K, 25% higher than purchase price, either because you bought it for less or due to market appreciation, then you essentially get all your $100K back.  

Essentially, should we take this step-by-step approach rather than jumping straight into being landlords?

Buying a multifamily property is essentially buying a business—income minus expenses.

It looked all very nice, but, I made a comment that there was a lot of windows and it was very easy for people walking by to look insideThe agent told me that windows and open spaces were now industry standard gyms due to safety issues.

Essentially - would not recommend at all.  

Ensure it meets safety and zoning requirements before using it as your primary residence to avoid violating any laws or terms of your owner-occupied loan. 

From your post you are seeking to essentially knock down the house and build brand new.

You can use recent purchase price and go up to 75% LTV with 650+ fico if property is 70% occupied with no health and safety issues.