Anyone can apply for a patent, but if you write a patent application on behalf of others as mentioned above, you must take the patent agent qualification certificate. You must graduate from a full-time undergraduate or junior college in science and engineering, and work for more than 2 years before you can take the patent agent qualification examination. Then you can get the qualification certificate.
As long as you can write, you can help them write, as long as you don't act as an agent and don't charge. Not if you want to get paid.