Family Influence... - buy some favours so you can use the local businesses.
Found the option! Was just unconsciously skipping the line every time, it appears. Here is the text:
As your family is wealthy, and with wealth comes influence and connections, you can spend 2 hours walking around the locale and calling in old debts and favours, or promising new ones.
This will cost your family 50gold spent now on notes of exchange and likely collected soon (for simplicity, the gold is taken immediately).
Using this option has a high chance of opening up the same features to you as if the region were part of an allied realm, such as the option to repair or entertain your troops or leave your wounded at the houses of healing. There is a small chance that you find no sufficient favours to call in, or that your business partners take the money and leave you dry anyways (with deep apologies and very believable excuses, of course).
So its as if you were in allied territory, so no bank usage indeed.
