There are plenty of cheap options. e.g. I'm using a Raspberry pi zero w right now.
Less than $15.00 and it will cover an RV but not a house.
edit
But if you want to attach a nas to it, it would choke.
I'll bet the zero 2 could do it. $15.00
here is the list of supported devices: https://openwrt.org/toh/start
And lookie here!! https://forum.openwrt.org/t/whats-your-favourite-cheap-lede-openwrt-device/1362