Once they're paid down their loans (and even before then) you should have a pretty good picture of their financial situation. What are they going to do with that extra cash they have now that their loans repayments are done?
* Take out a loan for a car/holiday?
* Open a share trading account?
* While they're paying down their debts can you get them a better deal on their credit card?
Pitching additional product for me is troublesome because of the intrinsic fees associated with them. I look at my service as something that accelerates debt repayment in the most efficient way. But to encourage customers to roll-over into a cc balance transfer, mortgage refi, or student loan consolidation, it just pushes their obligations further out in the future. Now, this might not be a bad thing for some people. But ultimately you could get a lot of people into the fee roulette game and it becomes a never-ending cycle where every economic peak and trough of high->low interest rates creates a new incentive for a financial services company to pitch new product.
So, I struggle with this. Do I want to maximize my revenue, or do I want to just provide a really good service for the small group of people willing to pay for it...
As a first-time founder and relatively new developer, I could never really tell when the time is right to stop creating and start pitching. Looking back, I definitely went too far with the build, but better late than never to snap out of it and start soliciting.
If none of your free customers are willing to pay, then it might be time for a pivot. Such as licensing your app to financial providers as a value add.