Hi
Many questions to ask and many things to be discussed about this piece of software ... What I have in mind is an online solution (web based, accessible through a web browser), don't know if this fits your needs but if you plan on reselling it, it could be a good way to have this SaaS platform. I'm heading for a PHP and MySQL platform, php code built on top of Zend Framework.I've built such systems in the past, with balance sheets, invoicing, payments (incl. downloadable PDF files for each, depending on my customers' needs). A couple of them hold millions of records after some years of life and still without any performance or security issues, most of them on private intranets inside customers' networks.
About the software itself and its functions, I think we should discuss and I should get some very detailed explanations about each and every part of it, so then I can properly estimate the amount of work involved, the bottlenecks or any other possible issues etc. And I think this should develop into a longer term work together. So please get in touch with me if you think I'm the right provider for your project.
Regards
Dragos