Configure Ssl For Multiple Storefronts

I run TWO storefronts on CS-cart 4.3x and Nginx. I'm trying to install SSL and encrypt both storefronts. After some study I still have no idea how to do it.

1. I suppose I need to buy a multi-domain SSL to work with the multi-store installation of CS-cart? Could you please recommend a cheap multi-domain SSL?

2. Is it possible to configure the free Letsencrypt SSL certificate for multi-store installation of Cs-cart?

Your help is much appreciated. Thank you!