You seem to be doing only general ledger accounting with the first iteration.

Accounting is a domain with tough competition from open source solutions (SQL-Ledger, LedgerSMB, WebERP among many others) as well as new SaaS services like freshbooks, lessaccounting etc. Just suggesting to have a look at those solutions too.

I would suggest to showcase a demo/trial without asking for credit card detail. Or at least make such a demo available for HN evaluation.