How easy is it to convert pure HTML/CSS/JS into React down the road, or should I not even bother? [closed]

I’m wondering about the easiness of converting HTML/CSS/JS into React, and if it’s feasible or not.

Here are my options for creating a website:

1. A friend of mine has offered to code the pages in pure H/C/J, and then we can hire someone to convert it into React once we’ve made some money
2. I can hire someone off Upwork to create the pages in React from the start, but this will cost me money upfront

Extra info: I do need them to be converted to react eventually

In general, is it feasible to convert HTML/CSS/JS into React, or is the process just entirely too cumbersome and I should just pay someone from the start?