We have been down your path many years ago. I look with envy upon your journey because, for us anyways, it was incredible how much we came to understand about ourselves, each other, our partner and even the world around us.
The common saying is that the first three rules of real estate are Location, Location, Location.
I like to say the first three rules of Poly (actually ANY relationship) are Communication, Communication, Communication!
My wife and I have said many times since becoming Poly that if NOTHING else ever came from our life change that we still have a huge benefit from all the communication that we have done over the past number of years.
I have said many times that there is no such thing as jealousy. Jealousy is simply fear. Fear of what will happen, what could happen, will he/she/they still love me, will I still love her/him/them? Open, honest communication will kill that emotion dead imho.
Finally, we firmly believe that Love is not a finite thing. Human beings simply expand the amount of Love they feel to encompass those that are giving them Love. If we are capable of loving multiple parents, siblings, children, aunts, uncles, grandparents, cousins then why wouldn't we be capable of loving more than one partner?
Enjoy your journey, we did.