Watching a tutorial on how the
Lightning Network works. Is it possible that only one party puts in money in the founding address / transaction?
The current protocol implementations only allow one party to fund a channel.
If only one party funds the channel, then the first payments can only be sent from the funding party to the counterparty. After that, subsequent payments could go both directions (until the entire channel balance rests with one party, at that point transactions could again only flow in one direction. It is not possible to have 'debt' in a channel).