The Millionaire Real Estate Investor book (Investor #34)

[Joe Demonte]

Hello,

I am currently reading the book The Millionaire Real Estate Investor and came across what Gary Keller calls "Story of Investor # 34".
Synopsis of story:

Investor #34 started investing by buying Limited Partnership Interests in real estate. He and his wife would obtain lists of the Limited Partners from General Partners (which, by law were required to share).
Then mailed those investors a marketing piece offering to buy their interest.At the time they would offer as low as $50.00 for shares that were valued at $100.00.

They did this over and over and re-invested by buying more Limited Shares. They re-invested in other areas of real estate that produced residual income (apartments/storage rentals).

What is this type of investing called??? "Buying Limited Partnerships"
I am new to investing in real estate and have been trying to research this type of investing... I cant seem to find what it is called, or if it is even a smart investment to begin with.

Anyways, thanks in advance!
Any information leading me in a direction would be a great help.

THANKS!