So the average player comes into play with roughly a throne and 18 rings worth of value, (less if you have a congregation more if you have a mana site.) Which you get at the start of an event. In addition, artisan potentially gives you some magic items to sell.
Now making a significant amount of money is tricky, but trading your resource for money and making a small profit should be possible. If you pulled off 20 thrones that would be seriously impressive.
I’d suggest that the 1 -4 throne mark would be more reasonable, 1 throne you should be able to easily pull off with anything but a congregation. 3 thrones would definitely require you having to make a profit, rather than just sell whatever you have as income. It’s worth pointing out that a lot of magic items fall into that mark, and having an outstanding contract for X item could give you more game, (particularly if you start with a business.)
Finding someone who is happy to start with your character in debt to them, should be reasonably easy, as you are essentially promising them free things for very little cost. I’d advise finding a way that on some level you are getting something out of the relationship.
In terms of debt enforcement, the reckoners in the league, potentially the threat of the Lictors. You might manage a civil case around a broken contract, but I’m not even certain around that. However, if you think this plot is fun it would probably work better to have a debt you are strongly inclined to keep. Perhaps someone saved your life purchased you from slavery and for cultural reasons you need to repay them. Perhaps you pawned a precious item as collateral against the debt.
Thoughts on why you accumulated that debt in the first place are probably important,
It’s also worth pointing out that a lot of nations have archetypes that are essentially traders on behalf of a group, with varying degrees of power within that relationship. Depending on what your long term aims are, this might actually be more fun than starting with a debt. It gives you a group, a clear IC thing that your money is going to, and will probably allow you to do more trading than you would as a solo player.
Dawnish Seneschals are a archetype that really work on the thankless trading job (https://www.profounddecisions.co.uk/empire-wiki/Dawn_economic_interests) although there are definitely similar roles in other nations