Hi Leslie,
I have done quite a few different JV deals with other Canadians buying US real estate, and each deal is setup different depending on the deal and the partners who I am working with.
You definitely need to talk to a CPA before doing anything in the US. Are you aware of FAPI and FIRPTA? If you are flipping properties, as a foreign investor 30% of the sale can be withheld by the IRS! So sit down with your CPA and figure out the best way to structure your deals with your investors and also the best entity structure for yourself. With the LLLP, each of your investors will be required to obtain ITINs and file a US tax return.
Also, LLCs are treated differently in Canada than in the US and are generally not recommended for Canadians buying US real estate. Canada doesn't recognize LLCs as flow through entities or partnerships. Instead it recognizes them and treats them as corporations, where you then run into double taxation.