I had the property manager to issue notice to tenants to stop flushing down baby wipes!

This is a very different model than the owning your own asset and managing yourself to optimize cash flow like in Short Term Rental Long Term Wealth, but it is a legit syndication.I have not personally invested with them but I know their head of data very well and I have seen that their underwriting is RIGOROUS.

Are they harder to manage than duplexes?

I'll say doing your research on landlord-tenant laws is crucial, consider property management if you're not into self managing your property, secure financing, crunch the numbers and prioritize location and property condition when searching.

Looks like I should have asked more questions :) Okay some of the comments are assuming you plan to be the main operator and you won't hire a property manager. 

Who is going to manage your properties?

Even if you create a non-CA LLC, if you are managing the business from California, you will likely be deemed to be "doing business" in California and therefore likely subject to CA taxes.

He acts as project manager, sources, finds the subs, and even oversees the staging.  

No property is perfect, especially an older one, but with good management, most risks can be minimized upfront.

The cost of entry is low, and cash flow is high.