I graduated from University of Southern California, Sol Price School of Public Policy with BS in real estate development.

Which insurance companies offer the best umbrella policy in California?

Adverse possession is the tool of last resort and often problematic.Every state has different statutes; I think PA's is (20) years.It IS the policy in all 50 states and commonwealths.

The landlord/seller must provide the Buyer with a recent survey or a current plat; copies of liens, restrictive covenants, and easements; a Seller’s Disclosure of Property Condition; a disclosure for nonsubdivision properties stating utilities may not be available until the subdivision is recorded; tax certificates; a copy of the insurance policy showing the name of the insurer and insured along with a description of the insured property and the policy amount; a seven-day notice letter; and an annual accounting that includes amounts paid, amounts owed, payments remaining, taxes paid, and the amount paid for insurance premiums plus an accounting for any insurance proceeds.

Bank policies may vary, but that's pretty much it. :)  

You will need both the CGL & the policy covering the property.Most property policies will exclude Products and Completed operations.  

@Tim Greenfield the 1-3 unit space can be written on both a personal and commercial policy.  

@Steven Hamilton II thanks for the info, after speaking with my partner on the deal it looks like we will plan to not LLC this deal and cover our selves with rental property insurance and possibly an umbrella policy if we feel the amount is inadequate. 

You can frequently get out of the penalty after it is assessed by swearing that you are now fully aware of the law, that you swear you won't break it again and that you are implementing policies and procedures now so that you will always be able to issue your required 1099s in the future. 

Get a good umbrella policy.