Website build: Red flags
Each of these signals has a mechanism behind it. They are not "beware of cheap offers", they are specific things you can see in the document in front of you.
What to look for in the document in front of you
An offer with no page list
If it does not state how many and which pages are included, the price means nothing. It is also the most common source of later disputes.
"Optimised for Google" as a feature
That is not a feature, it is work that continues for months after launch. Used as a bullet next to "responsive design", the phrase means nothing.
Design shown only as an image
Ask to see it on a phone before you approve. That is where most of your visitors will see it.
A total timeline under two weeks
Technically possible. It does mean nobody will write bespoke copy and nobody will think about structure.