Need Advice/Have Questions About Online Business and Website

Hello, I am trying to set up my own website for a business. Essentially, the business involves a user (customer) submitting certain documents and things for me to analyze. Then, I will provide a page on the website with my summarized analysis, for a monthly fee. I have been learning HTML, CSS, and Ruby, but I still feel completely inadequate when it comes to developing this website. One major thing I am worried about is the website getting hacked, since it will involve financial transactions. Also, I cannot afford to hire a professional web developer to do this for me.
So, I have a couple of questions. First, what is the best path I can take that will allow me to achieve my objective of getting this website up and running? I have been using Codecademy and it's alright, but I feel like I am not actually learning much. I have a strong background in inflected languages and so far learning to code hasn't been all that different than learning languages, but I am still lacking. If anyone has experience in setting up online businesses, what boxes do I need to check (things that I need to learn) to make this possible? What programming languages and what aspects of them do I need to familiarize myself with the most?
Secondly, and this is a more technical question, is it possible for a website to contain pages that can be accessed through an external link only, and not found internally? For example, the url link would lead to the page, but that is the only way for someone to view that page; they wouldn't be able to navigate to it from the website itself.
I appreciate the help of anyone replying. I am a big believer in the ability to figure out any solution on the internet, and hopefully I can get this website and company started. Thanks!

 

Here is a list of recent threads that may help you >>> https://www.digitalpoint.com/search/40222540/

Also look at https://cutcodedown.com/

 

The first link comes up error on my end, what exactly did you search?

I haven't seen that website before and it looks pretty helpful, thanks.

 

No idea why the link won't work for you. Works fine for me.

Anyhow, here is a list of results that the link pointed to:

https://forums.digitalpoint.com/threads/should-i-still-use-jquery-with-html5-in-2019.2857316/
https://forums.digitalpoint.com/threads/how-to-write-good-html-css-with-webflow.2857352/
https://forums.digitalpoint.com/thr...instead-of-learning-to-code-manually.2857358/
https://forums.digitalpoint.com/thr...css-by-hand-in-a-text-editor-in-2019.2857372/
https://forums.digitalpoint.com/threads/why-so-much-hatred-toward-html-css-noobs.2857373/
https://forums.digitalpoint.com/threads/html5-semantic-tags-fail.2857688/
https://forums.digitalpoint.com/thr...-css-approach-sucks-what-should-i-do.2857770/

Basically, they are all started by the same person wanting to learn the best way to design websites. They show the evolution of his thoughts starting from knowing nothing about web design until today. He started each of these threads in the order listed above and is in an on-going learning curve.

 

That's pretty helpful, thanks.

But if anyone has anything else to add, more directly answering my questions, I'd also appreciate that.

 

It would be helpful to have a better idea of the business you are trying to start, of course. That said, I can answer your second question: you can absolutely have as many pages as you want that are "standalone islands" on your website. It is easy to do; just put up a page and do not link to it from any public page on your website nor include it in your sitemap.