Heroku is the OG of affordable rails hosting. If the tutorial is older than 3-4 years ago then it was published when Heroku was free, which it no longer is.

There are lots of other affordable, but probably not free, options now;

https://railway.app/ https://fly.io/ https://www.hetzner.com/ https://www.digitalocean.com/ https://render.com/

Any option for local hosting for development purpose ?

Also what happened to heroku free ?

Salesforce bought it and there were too many freeloaders.

Options of "local hosting for development purposes"? Do you mean running "rails s" locally on your machine?

Yeah, on my machine .