How I find list of free guest posting sites?

Hello Dear Friends,
Please tell me how I find free guest posting sites related to health and legal niches.

Maybe you can try something like doing a search in Google with the phrase 'write for us' or 'guest posting' in quotations plus the words free and your keyword legal or health.

I am not an expert on guest posting but I saw some things like that when I was looking into it myself not long ago.

Still you can find out lot of guest post sites by searching with your keyword
your keyword(s) + inurl:write-for-us
your keyword(s) + guest-posts
your keyword(s) + inurl:guest-post-guidelines
your keyword(s) + become a contributor
your keyword(s) + bloggers wanted
your keyword(s) + submit an article
your keyword(s) + want to write for
your keyword(s) + contribute
your keyword(s) + become an author
your keyword(s) + guest post by
your keyword(s) + now accepting guest posts

Please inform me how I discover loose visitor posting web sites associated with health and legal niches.

You can use drop my link for getting the sites which will accept guest posts. Out of that some sites will accept free guest posting. So select that site and submit your content to that site