Developer for A2billing and WHMCS

We have a WHMCS and an A2billing installation and need to customize both. The process of invoicing, invoice templates, features in A2billing,.... We are looking for an experienced developer for an ongoing project since this is work in progress and will go for a couple of months. You need understanding of the systems and you need to be able to work on your own including testing and quality finish of all the customizing. We don't want somebody we need to "babysit". We want to give a task and get an already tested working result in return. We expect commented code and a good documentation in our wiki. This is an integral part of the job. Be aware that we are looking for an experienced person. We are not paying for training and learning (and we dont have the time for that). We will brake the work down into tasks which you will estimate in hours. We expect you to know the tricks and pitfalls of those systems in advance. If you have any questions please post I will then clarify. All the best, Alexander