Maybe its a basic question. But I am trying to find out:

Is it possible to dial in using a modem to another Computer behind an "VoIP
only" connection?

Szenario: home user with an internet contract that provides DSL. The phone
line bundled with the contract is established as VoIP. So no "real" land
line phone.

Is it now possible to create a classic dial in to a server?

Extension: would it be possible to do a classic modem-modem call back as
well?

(all this at low cost - no cisco routers or something)

I found some words like modem relay but I am not sure to be on the right
track.

P