Is this possible

Here is my current setup for my home:

VOIP line local and international

2 lines are in the home, 1 phone for each line.

Is it possible to have asterisk make it so only outbound calls go on the voip line (willing to go sip if needed right now it’s vonage line). The Only inbound line would be the Pots line (has been the family number for 5 years or so)…and have only have 1 line in the main part of the home? Also this would need to be almost transperent to the end users (family) as they are not tech savy. i don’t need an IVR, nor seperate extensions… I just want to cut down on the calls going out on the POTS line as it’s expensive to call outside of the calling area (20$'s a month when it’s accidentally used)

I have never done Telco setups before, but would like to play/have the chance to learn on this…

I would like something like this when done:

Asterisk 1 line to the rest of the home.

Yes it is possible, you can tell asterisk to dial out of the sip trunks for certain areas, and the fxo for other areas, just some editing of extensions.conf and some dial commands in your outgoing context
like for me 618 is local
exten => 618XXXXXXX,1,Dial(dahdi/trunknumber)
exten => _NXXXXXX,1,Dial(dahdi/trunknumber)
217 is not local
exten => _1217XXXXXXX,1,Dial(sip/trunk)
exten => _1NXXXXXXXX,1,Dial(sip/trunk)
this is a simple example but hopefully it will help