What is probably "cheating" are two factors, in my opinion.
I have very little knowledge of coding
It is one thing to design a website (which can be done in Photoshop, Corel, Ilustrator, Indesign, etc) and another to develop the site, which undeniably needs a basic understanding of some types of coding and markup (HTML is not coding, it is markup).
I am pretty sure that the terms and conditions of Wix do not include "taking" their templates to be used outside the site.
That said, on this planet, at this time nothing is developed from ground 0, especially websites. Developers take advantage of a lot of development already done. Frameworks, design guides, design trends, stock photography, stock images, fonts... and templates.
Make a real aggregated value to your work. If you do not aggregate "too much" creativity, you can of course charge your client for your "know how". But you really need to learn how to code. Again, you will be using a lot of pre-made resources, but you still need to know how to use the tools.
Part of this work could be taking the time to choose a proper template suitable for the client, considering both functionality and style. But either use a free one (with the proper credit according to the terms and conditions of the template) or a paid one.