It's hard to see the value proposition of a bespoke freelance programmer hourly billing application versus a general purpose book-keeping application familiar to accountants, backed by regular support, and having been debugged over many years of field deployment.

What makes your solution better than Quickbooks or GnuCash?

What percentage of the market for free-lancer programmers can a bespoke product capture?

Why go through all the development effort of a book-keeping program and then only target it at a very limited market?

Good luck.