Two DMs One Copy

My partner and I have had to move our games to online since the quarantine. We each have our own Roll20 accounts because we both play in each others games. Our friends have been great, very patient and accommodating. And one of our groups wants to buy the source books for that game on here! But what about the other game? We are both running 5e games, and it would mean buying the PHB, MM, XGtE, VGtM, and the Eberron book aaggaaiinn. We already have multiple physical copies of all of those here on our shelves. It is wonderful that one of our tables has organized getting money together for that and we are super grateful for them. There must be a way other than asking the other table for money... that feels awful... especially right now... especially when three years ago we pitched D&D to our friends leaning hard on how it was cheaper and better than a movie. 

If you both don't DM at the same time, Use the same account that has the books.  

OOOOOOOOOkay! I think I just figured it out! If I hover over a Player in my game it has "Promote to GM" as an option. So my players buy the books, and then my partner "Promotes Me to GM" then he can DM his game from my account. Right?

Or, you have the DM account and the player account and you switch to whichever role you are for that game.