It looks like there will be 8 prototypes in all.
Drone Footage Reveals A First Look Of Trump’s Border Wall Prototypes http://www.zerohedge.com/news/2017-10-18/drone-footage-reveals-first-look-trumps-border-wall-prototypes
Direct link to drone footage
https://www.youtube.com/watch?time_continue=19&v=bx0xRx_P-nw