I really love the mod Fast Travel Cost by Narue but I found it to be too exploitable. By simply not carrying gold in your inventory, you don't have to pay for fast travel debts.

I made a couple simple edits to the scripts to disable fast travel if you are not carrying more gold than you owe in fast travel debt, and to enable fast travel if you do.

A side effect of this mod is it should also bring more compatibility with other survival mods that might disable fast travel via script since this mod will enable fast travel with each opening of the map.

NEW: Due to popular (lol, only 8 endorsements cannot really be called popular) demand, I have added similar changes to RAB Fast Travel Cost by RossAdamBaker. Similar debt mechanic to what is written above except:

The main difference is that if you have any left over debt after traveling, the script will assume and state to you that "You were not sufficiently prepared for the journey!" and it will make a roll against the disease chance in the MCM to add a random disease. If you have disease chance set to 0%, you should not receive a disease for accumulating debt.

Requirements:
Either
1.)  Fast Travel Cost by Narue
OR
2.) RAB Fast Travel Cost (vanilla version only, iNeed version not yet supported with debt requirements) by RossAdamBaker