If you qualify as a accredited investor you might want to take a look at passive investing in syndications. 

Currently there are only options for accredited investors only.

The difference is CF and A+ can market to non accredited investors. 

My idea would be if 5 people wanted to put in 20k each, we could invest 100k in a fund, or possibly reach a higher level on a syndication which may result in a better distribution pay-out.What would be some of the true business/tax challenges others foresee in creating a multi-member LLC with other accredited investors so that we can pool have multiple members pool money together to invest in these 6-figure syndications and funds? 

I'm not a CPA, or Lawyer or Financial advisor, but I have invested in multifamily syndication as LP thru a LLC and will try to address your questions:1) As far as I know, the same SEC rules applies for all individuals in the LLC, meaning they have to be accredited investors (for 506.c offers) or sophisticated investors (for 506.b offers), besides having previous relationship with General Partner etc.2) It is your discretion.

Is this offering open to non-accredited investors?

But you have to be an accredited investor to access these.From a risk perspective, I'd definitley try to diversify geogrpahically and by property type. 

I have looked at Holdfolio because they don't require the investors to be accredited.  

Syndications may create UBIT.Publicly traded REITs are open to non-accredited investors.  

There are scam online schools out there, so you have to make sure they are fully accredited.