For startups, I'd try LivePlan or Upmetrics. Both have guided templates, financial projections and an easy setup. If you want something free, Google Sheets with a template from SCORE or the SBA works well for the numbers, and Notion is handy for goals and market research notes.
Start with a one-page lean plan, and test a free trial before paying.
I work at Zenkoders, and if you later need custom CRM development to manage customers, I'm happy to help.
