Cost wise, I recomend renting a VPS with monero in a country not part of 5 eye / 9 eye and privacy friendly.

If you live in such country, and have acces to an internet connection not linked to your ID, you can then buy some hardware.
But you'll need then to calculate the electric bill associated by running it h24.

Services like vocal / Jitsi / Matrix don't need huge ressource if kept confidential (sub 100 people using it)
So better an energy efficient machine (with low power consumption and low idle power consumption) than a beafy overpowered computer that will cost you a lot in the long run