Buy Thunderbolt 3 Laptop Now, eGPU setup later?

Is this a good idea for 3D animation and making games?

I wanna only buy a dedicated GPU later when I need it and can afford it.

But not only do enclosures + GPU cost a lot,
but TB3 laptops in general are expensive! And sometimes include GPUs.

I only need TB3 and a decent cpu like an i7-7500U.
(Ideally upgradeable to a super fast CPU, but I doubt that’s practical…)

Also, how long can I expect a TB3 eGPU-capable laptop to last?
It’d be nice if five years from now, my new laptop is still alive to use an eGPU and if TB3 can still handle the latest GPUs by then.

My budget is $700 to $1,300 Canadian

It goes up by $100 to $300 every two weeks.

Also, can I/should I buy a barebones laptop?

Thanks for your consideration.