Ultimately, as the customer you can demand that they make you a website out of baling wire and scotch tape.
This may decrease the number of people who apply.
I would suggest, if you have someone in mind already, that you discuss the purchase with them. If they want the script(s), go ahead with the purchase. A professional developer may look at the scripts and tell you that their functionality is replicated in some open source package.
You are free to do whatever you want, it is your business decision to make. However, you are presumably hiring the developer because they possess knowledge and skills that you do not, and it would behoove you to take advantage of the service you are paying for.