subdomains v multiple sites
 

i have about 10 site which are for many niche.
they cheap. .info and not get much traffic just long tail.

the domains expire soon and i the renewel costs are high.

i was thinking to use one domain (.com) with many subdomains. is it good idea?

it is a good idea to get backlinks to as many different pages within a single domain as possible. Sub.Domains are an excellent way to grow a domain.

We can get hundreds of one way backlinks to each of your sub.domains, using niche keywords, to help boost your overall domain authority. visit us at www.hardlinks.org

we are running a 2 for 1 special.

Hope that answers your question.

Have a nice day,
~Ray

If you target different languages and countries - Yes. Example: br.site.com, ca.site.com, ru.site.com, etc. On you home page you can have flags with different languages, pointed to this country sub-domains.