Is this easier to achieve under the multi-member LLC or TIC single-member LLCs structure?

It they are in the right neighborhoods then developers are coming in and converting these structures.

How do you know what structural problems lie in an old house (built in the '30s) which you've never been in? 

It depends, especially on how your business is structured, lets say you have a holding company.

I've got a lot of other contacts for GC's, Architects, subs, permit expediters, Geo/ Soils, Zoning attorney's, ADA ramp plan engineers, structural engineers, you name it related to new construction in Philadelphia.

Remember, the federal government does it's due diligence...this is a very structured process. 

Do you structure a line of credit or do they lend a percentage of your purchase price?

Am i able to build a one structure duplex/triplex if the space permits for it?

So I have a mobile home park I am trying to purchase. The seller is willing to let me take over there payments. How do I go about taking over there payments?

He has a loan with a bank also I'm located in Tennessee.

Can anyone advise the best structure for both tax and liability for Canadians investing in US real estate for buy/holds and flips?