Developing a Login Function

I am looking for advice on how best to incorporate a log in function for wholesale users for my site I am developing for the company I work for. For this site we are not selling direct to consumer, but would like to have an option for our wholesalers to be able to log in and view a version of the website that would have additional content that the general public are not able to view. I had the idea to create a sub-domain site that would look identical to the main site, but would have the additional content as well as WooCommerce for the wholesale parties to purchase and place an order. My trouble is trying to figure out the best way to set up this Log in function. I haven’t been using WordPress very long and have never had to build a site with the option for a Log in. Ideally I would also like to be able to have a registration page for new wholesalers to be able to set up an account with us. I would like to be able to confirm or deny their membership to the site, to have a fall back for weeding out spam, should other spam protecting plugins miss a few. Any help that anyone can give, I would really appreciate it.