Software Idea Bringing to Life in a commercial platform

I have a software idea that works on my clients plarform but I want to be able to bring it to life and commercialise it to sell it to other clients. I want to be able to create a document and a trackable link in a platform such as doc send (or proprietary but imagine that would be alot of work?) Then go to an email platform and be able to send the same link within an email but with unique tracking to each email address. My client uses post mark to do the email send and we could use the same for the actual sending with the follow up emails coming through to outlook / gmail etc I can show how this works currently on my clients platform but I want to build something stand alone that I can sell to my clients to do this so that I have my own SAAS solution. I need someone experienced to tell me how best to do this, how to build it and how to commercialise the front end to sell it? No current idea on costs but I don't have a huge budget.