Do you buy new hosting for every new site or you use subdomains?

I have a plan with Hostwinds where I get to host unlimited domains on it. The only thing is that I have only 1 main domain and rest are SUBdomains. However, I do get "xyz.com" in hosting but its also like "abc.com" is my main domain. So I can even visit my secondary website if I type "abc.xyz.com"

I am sure this affects SEO in some ways, does it have any major effects? Do you prefer getting separate hosting for each domain? What about CHURN and BURN?

What if I host CPA sites as my…

Do you buy new hosting for every new site or you use subdomains?