I am planning to go dynamo hub in the next few weeks. I did a scoping mission at one of the local bike shops. And I left a little confused.

They showed me a front light they just finished installing so I have no worries there. They are also super close to home and have done other work for me in the past.

They mentioned you cannot get a rear light if your bike hasn't been pre-wired/designed to support the rear light.

True or false? Is it possible to wire externally? Or too much hassle? Or something that requires lots of or different experience? Any insight would be appreciated!

The dynamo front light will make a difference, but I really need to get both squared away to be completely happy I hate having to charge lights!