This is a great topic. I am working on building a budget (ish) eMTB.
For the experts here, 6 months later, the recommendations still apply?
I know this area is changing quite quickly.
Would also be great to have oficial forum builds for types of board vs budget. Would great encourage beginners.
Cheers
The words cheap and budget are all relative to your personal situation. From my perspective I’d look at it from a safety point of view IE - Am I willing to risk my kids riding something shitty from AliExpress? The answer is no flocking way.
I’m looking down the barrel of a new build right now and here are my minimum specs in comparison to my current builds that’s sort of top end. Price is in AUD and don’t tell my fucking wife or I’ll cut you.
that’s a good reason to make a new board 
and use it more than your kids too