I find it depends what you want to do with those sites.

If they are for a client, then they can have their own VPS as makes billing clear and easy.

With team development I have maybe 6 Joomla/WP/Laravel sites on a $5 DO server. With Swop reasonable size it works fine when such low traffic.

Issue we his was available ram. With 3 reasonable size sites MySQL maxed out ram and strange things started happening. So depends more on your DB and memory demands and that is also influenced by traffic.

Bonus question: How many do you put on a $15 VPS?

When I freelanced, it was 1 to 1. I put it on the customer to sign up for hosting (often at DO), give me the credentials and I'd take it from there. As it was their account, I was not on the hook for doing billing, invoicing, making sure they renewed their services every year, etc... More importantly, if I no longer wanted to support the site, it could be handed off to another developer without me having to move the site from my servers, etc...

I'm old school - I prefer from scratch. Basic DO server, install everything from yum / CentOS x and write the code for it. Later in freelancing I starting doing sites in Wordpress because it made sense from a time / money perspective.

Personal work / side projects, I'll host as many as I can on a single server until the project gets out of the garage and needs it's own resources.

Hard to say anything. If you have 0 visitors you can have as many sites as the disk space allows. If you have 1 mio a month on each, then 1 site is probably all it can take.

don't have one but i worked for a shared hosting provider :)

check if its a shared hoster or a real vm.

in our setup we even created a docker infrastructure plus custom varnish instances so the users can have a different php version per docroot, a reverse proxy on mouseclick and backup snapshots and much more :)

still we had to restrict the concurrent connections and customize firewalls for the classic wp hacks restrict the apache reloads per minute and so on.... in short if you just want to host a standardized low traffic site :) go for a shared hosting site.

the same for vms just be aware that you are in a virtual machine which means its harder do dockerize if the provider doesnt want it :) but as a dev instance i do have a virtual and a root server :) so i can test distributed services :)

i personally administrate linux systems for years so i prefer root systems and the commandline :)

Thanks for your votes. That is really interesting. Please also write, how you do it. Do you install some cPanel to manage hosts or do you do it alone? Do you host the same type of Apps along a server? or also different ones?