The quickest way to enter a niche and start making money in that niche is to have something to sell.
It doesn't matter what business model you use... you most likely have some form of content or product that attracts the right people and then leads them on to a sale.
If you're a blogger ... you need to write interesting and relavent posts that attract the right people.
If you're a vlogger (video blogger) ... you need interesting content to talk about in your videos.
If you're a list builder ... you need to constantly produce interesting newsletters that keep your readers hooked.
If you're an affiliate marketer ... you need to create landing pages to increase your ad quality score and prime your visitors for the offer.
If you're a product vendor ... you need products to sell, and need to constantly develop your sales funnel.
Point in case, no matter what business model you use online you will need some form of content or product to help you make sales.
But as you already know, creating an info product that SELLS is hard. Because if it was that easy everyone would be making their fortune.
If you want to skip the development costs, cut the stress, and have everything that you need right now to start making sales then you'll want to make a start by using PLR content.