How many real estate investors (SFH) exist in 2020 in the US?

[Josh Miller]

Start with this 2012 post by Joshua Dorkens stating there are 28.1 Million "Real Estate Investors" in the US. Bigger pockets post

According to Biggerpockets stats https://www.biggerpockets.com/stats , over 1000+ new members signup every day and at the time of this post, they have 1.6 million+ members.

Jump onto Facebook and I see lots of investor groups in the 50k - 100k range but nothing larger.  

Talking to some real estate software providers, they have between 300 - max of 20k paying users.  

I am interested in finding out how many people are not "learning", but are actively looking every week for a new investment property to buy/flip/wholesale AND ARE ACTUALLY BUYING?  How many investors are purchasing multiple homes every year?  Does anyone have a good scale on this number or have any resources I could dig into?  

My hypothesis is the US has 30,000 active investors but it's just a guess so posing this question to see if anyone has done any actual research into this number?

As a side discussion. With 85-95 million SFH in the unites states, lots of opportunities. :)