You'll have to decide what's more important, having asset protection or having 100% assurance that your note won't get called.Short answer: consult your attorney.

It is bad enough to have one for each series of properties.That said search on Trust or LLC here and you will see it is an area where many have different ideas and the strategic set up between them seems to be different depending on which "expert" designed the strategy for asset protection or probate or?

@Jack Taylor - if you are more of a visual person, here are some diagrams that might help you further on this quest: Asset Protection Decision Diagram - to help assess the need for asset protection, and what to implement: https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-decision-diagramAsset Protection Onion Diagram - what, when, and at what cost one should implement in terms of asset protection - https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-onion-diagram-v2What is needed for complete asset protection OR the domains that need to be intersected to find asset protection - https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-spectrum-diagramHow a fully implemented asset protection layout might look. - https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-structuresIf you want more details, from an investor perspective, PM me. 

Is it better to move it under LLC for better asset protection or just purchase umbrella policy

There is risk to the seller of legal or regulatory action if the buyer, for instance, violates certain consumer protection or mortgage servicing rules or laws.

You can decide to pay him weekly on progressed work, but that’s just a headache, maybe milestone is best protection, or at least bldg inspection sign offs if you have that.

This should always be covered by your business/landlord policy as an investor, and it's most commonly called business income protection or loss of rents protection.  

As long as you maintain adequate insurance it is very rare to receive any benefit, tax asset protection or otherwise, from establishing LLCs.

and only after you covered the "other" aspects of risk management (insurance, umbrella insurance, proper property management, etc.).Here is something to help assess the need for asset protection, and what to implement - my Asset Protection Decision Diagram : https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-decision-diagram Asset Protection Onion Diagram - what, when and at what cost one should implement in terms of asset protection - https://www.biggerpockets.com/files/user/CosIorg/file/asset-protection-onion-diagram-v2 What is needed for a complete asset protection OR the domains that need to be intersected to find asset protection

Also a stance to not over look cash flow, tax protection, or debt pay down.