Portfolio deals. Is it worth building one with the intention of selling it off?

[Ryan Dossey]

I have seen several listings on here as well as CL. Do the guys that build up a portfolio and then sell the package make good money? I imagine you are trading (hopefully positive) cash flow for a lump sum pay out. I would imagine for it to be an attractive deal all of the properties would need to be under market value which means you would be buying them really cheap to start. I normally see these consisting of more low income area properties. Are they a good deal to buy? 

Way I see it as a seller: You could get away with including a few problem properties to get rid of. Instant capital to move to "bigger and better" things. 

As a buyer: Not having to build a portfolio slowly. I imagine going through and checking the numbers on each individual property as well as touring them would be a nightmare. 

What are your thoughts? 

example: https://stlouis.craigslist.org/reb/4617853325.html