This is one of my areas of expertise and I field that I love helping with, but I would need to know more details in order to assist - for example: what service does the user get? What's the industry?
The usual models are freemium or subscription or regular online packages sales - but again, it all depends what you're offering and to who.
Let me know more details and I can try an assist.
I've successfully helped over 300 entrepreneurs, startups and businesses, and I would be happy to help you. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david