Should I buy or build a website?

If you have time..built!
If your time can earn more money, buy!

It all depends.

1- Do you have the money to buy a site. If so how much? If you have 1k USD then best not to buy. If you have 30 or 100k, then you should buy.
2- Do you want to learn and take a year or to before making money? Then you may want to start building from scratch. This is harder, but hey you are investing in yourself.

Buying websites carries a lot of risk and it needs good experience to find out if the website is even profitable or is worthy of the price quoted by the seller. From what I have read in the OP, you need to be extremely careful as there are lots of scammers and they will make use of your lack of knowledge.

I’m currently building a site from scratch and it’s given me the opportunity to learn a lot!