Just want to give my general knowledge and opinion on this free announcement, plus some knowledge on Google Shopping.
They claim that they did this because of the impact on small business owners and e-com sellers during the current pandemic.
We know Google plays the long game, and this will probably transition into paying to "boost" your free listing, just as a Facebook business page post slowly lost views over the years. For now, let's enjoy the free listing.
Although they claim that you don't need an ads account, they are still keeping the regular Shopping Ads above the fold of the free listings. IMO, Shopping Ads are the most powerful type of ads for ecom. Sometimes, they're the only ads with a positive ROI that I've ever seen.
I recommend signing up for Merchant Center ASAP. I can't recall exactly, but there is an approval process for either Merchant Center or your Product. It could be both.
So, you'll need:
Merchant Center account
A Product within Merchant Center
A Product Feed within Merchant Center (either linked to your website, or a manually fetched Google Sheet)
Google Advertising account (optional)
Shopify (optional)
https://support.google.com/merchants/answer/7052112 is an example of how many data fields are available for your Product.
You can download the data feed template, or Google Sheet, inside of Merchant Center, but it's different for each country.
Shopify is the easiest way to get onto Google Shopping, as they automatically send Merchant Center all the necessary information about your Product. There is an app on Shopify for Google Shopping integration, but it's hit or miss. I usually do things manually, which involves uploadloading Google's CSV template it as your Product Feed.
As of now, Google isn't even answering their phones due to the hype surrounding this, so get in early!
That being said, I'm here to answer any questions.