If you have bike skills, consider a kit. You will be spending ¢¢¢ or maybe $ on ebikes, rather than $$, At worst, you give it away or sell it w/o losing much money. Buy a good battery and you can use it elsewhere.

I'm seeing products on amazon now that now have wiring packages like production ebikes, as opposed to the junky connectors that required more electrical skills to figure out and assemble.