so basic requirements for the Facebook app:
it should be a native Facebook app to be used on Facebook web version but also inside Facebook Android & iOS apps
It should basically provide the same functionality you can see on https://www.cars45.com/.
Its a wizard based booking process for a car inspection appointment
step1: fill in some basic data and on every select read the options for the next dropdown from our API (like select „BMW“ as a brand -> load the BMW-models from our API). You can check the API directly from the chrome inspector, its public
step2: show a price and allow the booking of the appointment. also apply the dynamic dropdown logic. There is no need for fancy map display of the locations, just dropdown is fine
step3: have confirmation page repeating some of the data and some hardcoded text about which things to bring for the inspection
Designwise it should be super simple and clean, no animations etc. needed

comments: had a discussion with him on whatsapp call. need to share high level ballpark and timeline. 
jan 8th: have shared a ballpark of 20k USD. he said its 10 times his expectation. he is looking for 1-2K usd budget. lost lead.