They are likely to be cheaper and may do a more thorough job than the big companies, but I cannot endorse any one of them. 

Check out a few free sources I suggested in this post: https://www.biggerpockets.com/forums/32/topics/778471-commercial-real-estate-investing-coursesNote that I am NOT endorsing any particular platform, nor sponsors/operators that use them. 

Both Guard and Travelers write owner-occupied HO3 with the broadened home-sharing host activities endorsement, so you're not really making a big change. 

For a structure that currently exists and you are rehabbing the property, I'd recommend getting a vacant policy that has a builder's risk endorsement.

Gingrich endorsed it, DeMint endorsed it in 2007.

Rental dwellings can be scheduled on a single commercial policy and you would just endorse every future purchase to that policy.

Call a few new independent insurance agents and they will have Homeowners policy options that will offer the STR endorsement. 

There are a handful of carriers out there right now with more carriers adding endorsements to coverage SRT since they are becoming more popular. 

So you get potentially more coverage.If the Blanket endorsement is not available in CA, then what he is saying about adding to his policy is correct, each additional insured would have to be an sepparate endorsement to the policy and might be charged for (here it could be $50-$100 each)If you do not require the additional insured status, you should see if the company will notify you of cancellation. 

You could bring in a money investor for each new unit and manage it for a fee, or you could utilize one of the peer to peer lending platforms to borrow more capital to deploy.This is in no way an endorsement of the arbitrage STR strategy.