@AudioNut 

1) No.

2) You can use the same WIFI userid and passwords since they are not in the same WIFI area. For security reasons, using a different one is a better option.

3) Yes. 
 

4) Although I have not used one, consider a travel router to see if it is a better fit. They have more connection options.
 

@ArcherC8 

So to answer #1 and #3, would it be "no" because in this situation there is a different cable/wifi provider up north than there is here in Texas? Or is there some other reason? I do not want to inadvertently knock the router up north off line somehow.

I just thought of another question. If I had to or wanted to, is there a way to somehow log into the router up north is there a way to do that?

Unrelated, but, I wanted to copy and paste some stuff here instead of re-typing, but the menu to copy and paste doesn't appear with a right click of my mouse here for some reason. Any ideas how to copy and paste here?

@AudioNut 

Number 1 would be no in that they are two separate routers so what changes you make up north doesn't reflect the one in Texas.

There is another way to log into the router remotely without using Tether.

Here is a guide to set up the remote management using a web GUI rather then Tether: https://www.tp-link.com/us/support/faq/1553/

To copy and paste try the keyboard shortcuts like Control+C (Copy) and Control+V (Paste)

@AudioNut 

You could be with the same provider, in fact have two or more lines into your house on separate routers and they would be handled separately as they will have different IP addresses from your ISP. Think of the IP address from the ISP as being like a phone number.  In the router, you have an IP address for each device (something like 192.168.0.105) which is sort of like a phone extension.

Now if you used the same WIFI SSIDs in the same WIFI space/area from different routers could cause an issue. Since WIFI signal is limited maybe best case 1/2 mile, that would not be an issue in your case.  If you use different SSIDs on each router, there should be no issue having two routers in the same house.  Bear in mind when two routers are close together, using the same WIFI channels, they can cause radio interference with each other.

Many routers have an option to allow for remote sign in.  See your user guide. Most turn it off for security reasons.

I have an Apple computer and I just highlight the text I want to copy, use command c to copy and command v to paste. Also if you sign on to this forum, click on your user id (top right) you get a selection where you can see your previous posts.