Making an app that sells mutual funds is not very different from building an e-commerce app. The bigger questions how do you take it to market? How do you compete with the biggies who have been doing it for years and have big budgets for marketing and technology.
And if you decide to sell direct mutual funds only, then how do you survive the initial years since there is no ‘commission’ money to cover basic expenses?
So the core point is that making something is much easier than making it pay, in a scalable manner.