One Internet connection - Two Private LANs Question

I just read the little how to on one internet two private lans .

since this how to is a few years old , is this still the best and easiest way ?

setting up this way I see a double nat . but I do need to read it in more detail .
but assuming your ISP allowed two ip's at no extra charge , couldn't you just use a gigaswitch ?

isp modem - switch -LAN 1
-LAN 2

I was asked by a family member to found out the best way to set this up .
one LAN needs to be...

One Internet connection - Two Private LANs Question