Document Creation and Accounting Program

I require a “program” whereby I will fill out an Intake Form that will include the Business Name, Address, Phone … possibly 10 different fields that will then be used to “populate” or create: 1. An initial letter 2. An Agreement between the business and our company 3. An invoice generated later 4. A reminder email or letter for an overdue account Presently, I have developed these letters, agreements, and invoices in Microsoft Word. I would consider this “program” integrating these “Word” documents, or you might wish to create them in Excel (because there will be the need for accounting formulas and tax calculation), or you might wish a different standalone relational database program. I’ll need to see which companies have outstanding balances and how old the receivable is, and then generate a facsimile or email (with the invoice attached) I’ll want to be able to sort and generate reports by the various fields. I’ll want part of the program to be able to create checks and print them along with an envelope.