AskHN: how do I start development of a web app?

My small company needs to develop a web application to better serve our customer. It is a simple portal with users accounts and a personalized dashboard. The idea is to develop it little by little and integrate more services into it in the near future. My two questions are:

- How do I go about finding the right person/team to work on it and be sure they will follow through?

- What language/platform should I request?

- realistically, what kind of budget should I start with?