Just for comparison, my VPS server has ~20 active email boxes (postfix,dovecot,spamassassin,clamav), a few small-ish active wordpress sites (apahce,php-fpm,mariadb), radicale and some other smaller services running with 2 cores and 4GB RAM and it’s mostly just fine. Occasionally, specially during heavier updates on wordpress-sites, memory tends to get pretty full, but it’s still just fine. Tweaking memory cache for php (or running something else than php) would increase performance by a lot, but even without optimization the 5€/month VPS is quite capable to keep your internet presence around and on your own hands.