Hey that's cool, take your time no need to rush things :)
Ex-game dev here, for them to make multiplayer it would be extremely difficult and expensive depending on the method. If they use p2p (free, player to player)
then they would encounter bugs such as seeing the other players cursor or overlaying UI
If they used a dedicated server, it would cost them alot of money. (My game deceit my team was having to pay a few thousand dollars on servers)