Build a Sourcing Tool

I have 3 separate, but similar projects. All projects are a procurement sourcing tool (like freelancer). The buyer is going to be a county and there needs to be a hierarchy of buyers. A buyer needs to be able to post a REQUEST and receive many RESPONSES. A buyer should be able to have one request (with multiple line items). One line can be awarded to an individual vendor. So if a buyer posts 1 request with 3 lines, there could be 3 actual orders derived from it (if 3 different vendors win the bid). The finalized order needs to be able to send to another system with no additional charge. I also need to be able to report on all transactions as well as easily retrieve data from the system (at no cost). This is for government clients, so it needs to be secure and done correctly. No payment gateway is required. All finalized orders will be paid with purchase orders. Vendors need the ability to sign up for the individual site. I would need a quote to build this out as well as monthly maintenance. I also need documentation and training materials on using the software. The 3 projects vary in size. Each project is for a different client and needs to be built seperately. 1. able to process about 200 million to a billion dollars a year (500-2k orders a day) able to have 1000 buyers and 20k vendors and support for user management and security need 99.9999% up time with a fee everytime the server is down (so to encourage uptime). 2. able to process about 50 million to 200 million dollars a year (100-500 orders a day) able to have 1000 buyers and 15k vendors and support for user management and security need 99.9999% up time with a fee everytime the server is down (so to encourage uptime). 3. able to process about 5 million to 50 million dollars a year (5-100 orders a day) able to have 50 buyers and 10k vendors and support for user management and security need 99.9999% up time with a fee every time the server is down (so to encourage uptime). I am working with 3 counties (very different who need it implemented at 3 different locations. There will be no payments until the software is ready for testing. Once it good to test with most functionality build, I will pay 25%. The next 25% will be when all those change requests/fixes are done. The next 25% will be when the program goes live to a small group, and the last 25% will go whenthe project is finalized and all users are using it. After the full 100% is paid, the monthly maintenance will start. Please keep that into account when bidding. All bidding and payments will happen through the security of Freelancer.com ( until maintenance contract kicks in) Thank you.