I would like to find out if there already exist any APIs etc., to offer such a service. As part of my service: I would like to confirm affordability of users before purchasing a high valued product or service via my platform.
If you're looking to build a service like Xero that imports users bank transactions and balances, you've got a few options.
Xero uses Yodlee on the back end to power their bank feeds. As I understand it, it's rather old school and often errors out, but supports a huge range of banks through scrapers, private APIs, and all kinds of proprietary technology.
You can also check out Plaid - you can think of them as the modern version of Yodlee. They support a more limited number of banks, but have an excellent API and SDK, and I believe are much more affordably priced than Yodlee.
Xero is an accounting system, so likely people opt into their service individually + that individual user's data is never available.
Companies like Xero + PayTrust + NetLedger + etc... all have a fiduciary responsibility never to share their data.
I'd recommend using Facebook or Traffic Oxygen audiences + do some test ads.
Likely this will give you some great info.
Alternatively, you can speak to groups related to your niche. You can locate these through Meetup or CoWork sites or searching for conferences in local area.
Good rule of thumb. Stand up in front of a local group + make your pitch. If you can sell anything face to face, likely you can convert your pitch to only copy + ads easily.
You can use your talks to refine your pitch/copy.
I've done this myself for decades + taught this technique to many folks.
Easy way to master this... Talk to 100 groups + if your swamped by prospective buyers, you have a winner.
And if you hear yourself saying... "That will never work with my product... It's to unique/special/expensive..."
My guess is you require working with someone who knows nothing about your product to identify groups for talks.
Many times product developers are to close to their products to know how best to sell their product.