If you want low-level access to the hardware for reprogramming the stability routines, then any hobby racing drone running the CleanFlight or BetaFlight (https://github.com/betaflight/betaflight) software would be good... They can be built for under $100. However the camera won't be accessible by the flight controller.
If you only need high-level access to a flight API - e.g. sending commands like "take off" and "forward 1m", then take a look at GoBot: https://gobot.io/documentation/platforms/ - they have a few quadcopters on their supported platforms list.
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If you want low-level access to the hardware for reprogramming the stability routines, then any hobby racing drone running the CleanFlight or BetaFlight (https://github.com/betaflight/betaflight) software would be good... They can be built for under $100. However the camera won't be accessible by the flight controller.
If you only need high-level access to a flight API - e.g. sending commands like "take off" and "forward 1m", then take a look at GoBot: https://gobot.io/documentation/platforms/ - they have a few quadcopters on their supported platforms list.