Good afternoon.
I am considering building a power drone which could lift 3kgs.
Now, I think it needs: a flight controller, a RX, 4 engines, 4 ESCs and a large battery, plus a video TX.
The frame would be made out of plumbing pipes (PVC tubes, assembled in a square).

The Flight controller can be found at Aliexpress for some 40 €, the motors, about the same. Escs are also some 30€ / pc.
TX would be either my Frsky XE or a Radiomaster TX16S.
Rx : to be defined.
RF range: less than 1 km.
I already have most of the parts in house.

Is it so difficult ?
What are the caveats ?
Thanks !