Firstly, it's going to cost you money to publish this book and it could possibly sit on bookshelves for a long time before it's successful. Harry Potter was published in 1997 and the movie wasn't made until 2001. I'd argue that a lot of Harry Potters success came from the movie pulling it into the public's eye.

So with that it mind your friends telling you to make it an online book is honestly probably your best bet.

It's extremely cheap to start a website and it will help you generate a following. You can start by advertising for free on sub-reddits that pertain to whatever genre your book falls under. "Hey guys I've been working on this fantasy fiction novel for two years and today I just posted my first chapter at X website, give it a read and let me know what you think!" If people like it they'll tell their friends and so on and if they really like it they may offer to buy a copy. If it blows up enough a publisher may seek you out to make it official. Take the Light Novel series "Overlord" for instance. That series was a web novel/light novel long before it was popular and now the author has a manga and anime being published from it. It took several years for it to happen but the success came from his fans spreading the word.

Books don't become popular over night; that's the cold truth. And today electronic books are far more popular then hard books.

You'll have to put in some effort if this is something you truly want to pursue and with no income you'll have to make sacrifices.