@Sushil IyerWith my experience, to analyze properties effectively, you can start with resources like MLS listings, Crexi/Loopnet, tax assessor websites, or paid tools like Costar and Reonomy.

What matters more is whether the borrower in question has the (i) time, (ii) contacts, (iii) experience, and (iv) ability to effectively communicate & package their loan request to banks & credit unions in a way that is compelling to those lenders. 

I was mainly thinking about the effects of putting an entire strong cashflow back into the mortgage.

You will have to do something unique to make it effective & useful to you... because it's always no pain, no gain!

How do I design a small yet effective real estate portfolio?

It seems like a more cost effective way to have multiple tenants. 

You have to keep in mind that a plex will never be valued the same as an SFH, and renovations may not have the same effect on the value as an SFH.If renovations are not needed right now, I would work toward getting the rent to market for the as-is condition and then renovate each side when you have turnover. 

It binds the landlord, but honestly has little binding effect on a tenant when they simply choose to leave.

It's a type of house hacking that's very effective to get your foot into the real estate investing door. 

Flipping can be cost-effective due to lower entry costs and growth in neighborhoods.