I am a complete noob, but I felt that being able to correspond freely by phone/text *without* having to worry about what messages/images someone might see on my original mobile phone was important, so I opened a new, separate, full-fledged mobile phone account.

I investigated burner phones, but I think they do not provide functionality (texting, camera) and can still be expensive.

You should never use your main cell phone as your hobby phone, it's safer to have a burner phone, either a pay as you go phone or just activate some cheap phone on your cell phone account, of course this depends on if you have a need to hide this hobby from a wife/gf.

I've started using the Sideline app on my phone, which lets you choose area code. It handles calls and texts. I also use it when I sell stuff (crap from my garage, etc) on Craigslist, or at least that's what I tell my wife. Whatever you use, just delete everything constantly.
I haven't used Google Voice, but Google's habit of saving data makes me very nervous.

has everything my RL phone does, same brand & looks quite close.   It provides some protection.  Best to buy with cash & register to a false address.  
You should also use a separate hobby email.