Whichever is cheaper, most convenient, and provides all the services you need.

When I created the entity (an s-corp), I had to sell the properties from the partnership to the s-corp entity costing me over $10k in Realty Transfer Tax (I understand PA is one of the worst states in the union for this with the tax rate at 2% of market value or sales contract, whichever is higher).

You could have it call your cell phone and business line/home line simultaneously and whichever phone you pick up first that is the line you will take the call on...

More realistically, I'll typically do a deal that generates a 15% return on sale price or $15K, whichever is more.

So at the end of the day if you'll end up with the same rent ready product that you need to pay a property manager to manager pick whichever one is priced better. 

Make sure whichever you are considering that you thoroughly vet, include a visit to the market and a face to face with the provider. 

Whichever county agency houses the recorded deeds will have that public info for you.

Whichever one you decide on I highly recommend not getting stuck in a quickbooks/XL hell :).

As they would be working with marketing-critical to my business-I could be taxed in both the US and whichever country they are located.How do others deal with Virtual Assistants' taxation?

Hold him responsible for all rent payments until a new tenant is found, or the end of his lease, whichever comes first.