Are you thinking of combining funds as a partnership, or would they be simply a lender? 

In a limited partnership the "general partner" calls all the shots.. 

Would love some tips when it comes to pulling the trigger and buying that first property.

We have been saving for some time now and are ready to pull the trigger on the right deal.

I know I need help with the down payment, maybe through partnership or a gap loan.

Look into and discuss family limited partnerships with your advisors!

I was almost able to close a delayed financing loan with them (to get my cash back out from a cash purchase without having to wait any seasoning period), but it ended up not going through since the cash I used to fund the property came from a partnership, and I was applying for the delayed financing in my personal name (doing this to get lower rates, then will deed the property over to the partnership's LLC).  

If all goes well, I'm sure we could do the same deal again on a different property.Any reason not to pull the trigger on this one?

There are no standards for partnerships like this. 

There's a very reasonable chance they aren't allowed to sub-lease and doing so could trigger their due on sale clause.