Google webmaster doesn't allow you to create sitemap for up to 500 pages you need use paid method for that then have option to for single XML sitemap for one page.

I also create for my client website use this method.

For a website so large as you describe you likely have pages arranged into separate directories or folders. Usually a sitemap for each directory is created as an index for sub-sitemaps so for your site at example.com you would have sitemap-index.xml in your root directory that lists the additional sitmap-index.xml files for each folder.

There are many free and paid solutions for creating sitemaps, depending on the structure of your site. Is this a site of static html pages? A WordPress site, or Joomla? The best solution depends on how the site is built.

@murcy, it appears someone might have given you erroneous information, there is no 500 page limit and no requirement to use a paid solution to create a sitemap.

I believe the "limit" is 50,000 urls per sitemap.
The sitemap cannot exceed 10mb uncompressed
If more than 50,000 urls, then a sitemap-index to
A maximum of 1,000 sitemaps of 50,000 urls each
That would be 50,000,000 urls.

Your sitemap-index will point to where the other sitemaps are located, which can be anywhere on the site.

That said, making that kind of sitemap may not do as you wish as it is unlikely that g, or anyone else, will index all 50m urls.

Better practice is the top 1,000 to 10,000 urls (which surely have their own internal links that will get crawled) and if selected properly, should highlight all the important parts of any website.

If you want to handle big sitmap, talk to your cms provider and get plugin or tool.

If you are using WordPress Plugin, then you don't need to do it manually, Just install the WordPress SEO by Yoast plugin, it will automatically create a sitemap file for your blog/site. If you use others CMS or Manually developed CMS, then you can use some third party website to create sitemap file.

Generating XML Sitemap for larger website is not a difficult task as mentioned. Nowadays, there are many third party tools available which can help to generate Sitemap for 'n' number of URLs.

Also agree with 'drinstech', if your website is present on WordPress you can generate the sitemap using Plugin provided - WordPress SEO by Yoast.

Let me know if you need any help to generate the Sitemap. You can share the website URL as it will help to assist you further.

No need to create a single sitemap. you can create multiple sitemaps. Create one sitemap for each category or services. You can read online about creating multiple sitemap and naming convention.

If you want to create a sitemap for thousands of pages that you need to make multiple sitemap or you can use paid sitemap for unlimited pages.

I think your question is somewhat confuse, but freely you can create upto 500 sitemaps for each subdomains, no need to create more than one for each website, if you have subdomains you can create and submit