Can I use 26" electric hub wheels on a vintage road bike? I got this old road bike that I bought for $20 and fixed up a bit.  I'm having to use it for a very long commute in the meantime until I can get other transportation so I was looking at a cheap electric kit solution.  The mid drives are too expensive because my budget is only about $400 so I was looking at hub drives but all of them I find are 26".

My bike currently has 23.  The side of the tire says [700 x 23C]

If I get one of these 26" hub wheel kits will it fit my bike?
It's quite unlikely. The axle length (hub spacing) will probably be rather different. 

Here's a list of axle lengths. The same page also discusses how you might get away with it on a steel frame with quite a lot of effort. 

Then you get onto the wheel building, which isn't easy and had to be good for electric wheels with their greater stresses. The 26" wheels wouldn't reach your brakes, so I assumed you use the hub motor and your existing rims with new spokes.