We're doing about 40 rehabs a year and 20 new construction homes a year and would like to know if you think we should keep everything under one company umbrella or separate them.  

Keep your property in good repair, have landlord/homeowner insurance, and get an umbrella liability policy. 

Insurance would cover it, I would pay the deductible, and no assets would be lost.If you are in an area like San Diego where people are more likely to sue, a judge is more likely to find you guilty, and the payout is likely to be higher, then you may consider an umbrella insurance policy.

How do you know how much of an umbrella policy to get?

Insurance isn't crazy at all - I added a small umbrella plan to supplement AirB and B's policy.Aesthetic, ability to host small families (3-4 people comfortably) and marketing will be key/everything in Levenworth.And yes, a local neighbor, or responsible HS or college kid who wants to make $20/flip is key. 

For asset protection, if you choose not to do a LLC, you can just have an umbrella insurance policy.

The agreements make sense, but if I purchase solo under my name I can just get umbrella coverage for the property and be secure?

@Jeff Goedeker Disclaimer: I'm a former tax accountant, so this is just a suggestion and not a tax advise.In order to 1031 from sfh into mfh (syndication or not), sfh has to be part of the same portfolio under the same LLC umbrella.

Lots of BP podcast episodes concluding that this sort of corporate veil is easily pierced and that you can use an umbrella insurance policy for greater protection than without it. 

I don't use a LLC, just a personal umbrella insurance policy, and the taxes are done on Sch E.