We do get a better fee/split structure, and that's a fair trade for the extra work of managing a large investor base and it's associated extra accounting and tax reporting overhead.I also find the advice in the OP to be contradictory. 

However, I’m not entirely sure how to structure a syndication for these larger deals.

What entity structure is best for my specific real estate investment needs?

The question is how we can structure it in a way that is workable for both of us.

I like this platform on BiggerPockets which allows people to connect with one another in a structured manner.

Crime is a concern, but I'm thinking with the appropriate limited liability and insurance structure this could provide a reasonable shield.

Like you mentioned and what I've read is the deal structure and sponsor carries the biggest risk so thank you!  

Hello,Seller is willing to use creative financing to structure a deal with me.

The clear and obvious answer would be to instantly pay the back taxes and offer a small lump sum for them to move with and just lowball in whatever structure works for the both of you weather that is a better sale price or a greater monthly payment to them and just find your middle ground that works out for you both.

if Yes, what should be the structure, should he live rent free in return of the work and hours of work he provides?