On what CMS to make a site?

Question

CMS

You need to make a volunteer (free) site with ads. Advise CMS and plugins for it. There must be private offices. Logged in users will be able to post ads for a period of +-30 days. Ordinary users leave requests (comments) on ads. Visiting (planned) about 100-200 people a day. You need minimal costs for both maintenance and creation (since there will be no money for administration or creation), and as much as possible all processes should be automated, but not lost in safety.
And another question. How much hosting in terms of resources will you need to buy? There will be about 500-1000 personal accounts. How much does one user occupy in the database with a dozen text files and two dozen photos?

Answer 1

How much does one user occupy in the database

How much what? And it all depends on how much data is associated with the user, plus the database architecture that this or that CMS will impose on you.
Files and photos are generally not stored in the database.
This is a very small load, any server capacity will do, but depending on the gluttony of the selected cms
PS: given your questions, I highly recommend not doing this on your own. A better way for a public organization to find a sponsor. Or money or a company or a freelancer who would do what you need for free. At the same time, the site could remain in the use of a freelancer and he would put up his own advertisement, for example, in order to recoup hosting.