Cześć!
I can offer you a simple yet powerful solution, web based, so you can access your data from anywhere, with any device (computer, mobile, tablet).
It will have secure access with users and passwords, admin & employee roles, so you can keep your data safe. It can be stored in a free hosting or with a small monthly fee.
You will be able to register client data, car fleet data, print contract (with different types of contract), follow delivery and return dates, list available cars for a date range.
Scope of the project might be larger or smaller, according to your needs, also we can agree on different stages, starting with only 1 admin user, then employee user, and also the customer might have online access to do reservations! (or integrate reservations with your current web site).
Let's talk anytime soon so we can work together in your project. Feel free to ask me any detail you want to clarify.
Technology: web2py python based with mysql db.
I'll be pleased to work with you.
Best regards from this Argentinian-Polish developer ;)
Esteban
ps: this bid will be adjusted after agreement on the scope of the project, waiting for your contact