Marketing agency owner looking to start an industry specific CRM software.

I have experience starting and growing a marketing agency specializing in web design and development , SEO and hiring people for these specific positions.

I know nothing of software development or the costs associated but I’m interested in creating an industry specific CRM to serve as an all in one, lots of integration api with other platforms. The industry we’d go in is one of our niches for marketing so I have a good idea of the gap this app needs to fill.

Looking to find out more about costs associated with crms , potential pitfalls of such project ?