So I realize that's a pretty vague statement, but I know so little about electric bicycles that originally I posted in the motorized bicycle section not realizing they were different. 
Should I get a kit? Would that be cheaper? Is it complicated, or easy to make mistakes, I'd rather not have to tinker around with it later if possible?
The info:
I'm pretty tall
weigh over 200 lbs.
Don't want to renew my license (so must be legal w/o one and somewhat standard so I wouldn't get "profiled")
Eventually I plan to move to the city (less hills and probably less distance too) but right now travel time to my current work is 6 miles.
I grow (legal) plants and would like to if possible (when/if I move to city) to get a small cart to transport potted plants to give to friends or could also use for grocery runs, (pending if this is even legal, and possible w/o straining a motor or something).
my made up budget $800 or less (unless it would need to be more for a reason)
And probably looking at getting a used 10 speed bike to put the kit on if I go the kit rout.
I really don't know much about these bikes, I think I'd need more Watt's or more powerful batter to lug extra weight (my own and if I could do a cart), but if someone could tell me:
Here's what you'd need for your situation (parts etc). Here's a link to instructions (pending that its doable, not a mechanic, but I can tell blue from green wires though
) and here's around what it would cost.
Then I'd order the parts and build it, or here's a premade bike brand that meets those needs that you can look for in your area.
The cart idea would look something like this.
But instead of gas and kids in the back it'd be a small cart with 6-10 potted plants or something.
thanks for the help.

Should I get a kit? Would that be cheaper? Is it complicated, or easy to make mistakes, I'd rather not have to tinker around with it later if possible?
The info:
I'm pretty tall
weigh over 200 lbs.
Don't want to renew my license (so must be legal w/o one and somewhat standard so I wouldn't get "profiled")
Eventually I plan to move to the city (less hills and probably less distance too) but right now travel time to my current work is 6 miles.
I grow (legal) plants and would like to if possible (when/if I move to city) to get a small cart to transport potted plants to give to friends or could also use for grocery runs, (pending if this is even legal, and possible w/o straining a motor or something).
my made up budget $800 or less (unless it would need to be more for a reason)
And probably looking at getting a used 10 speed bike to put the kit on if I go the kit rout.
I really don't know much about these bikes, I think I'd need more Watt's or more powerful batter to lug extra weight (my own and if I could do a cart), but if someone could tell me:
Here's what you'd need for your situation (parts etc). Here's a link to instructions (pending that its doable, not a mechanic, but I can tell blue from green wires though

Then I'd order the parts and build it, or here's a premade bike brand that meets those needs that you can look for in your area.
The cart idea would look something like this.

thanks for the help.