When you say “I’m building a house” what does that actually mean?

If you are using one of the large builders you have some obstacles that will likely preclude you from achieving your goals.

If you have a builder constructing your home on the property you own, speak with your builder. He likely has experience with a low voltage company that can set you up with what you need and will know how to work with the builder wo conflict.

TP-Link AX3000 ~$150. Excellent range, wifi6 and very reasonably priced

The barn 100% needs its own ground rods tied to the panel you tied power to. Depending on what the “barn” is you may have additional grounding that needs done. My outbuilding for example is a pre engineered steel building. I needed to bond the building to ground as well.

Get an electrician to evaluate your barn electrical installation.