Humidifier? Pros/cons-Mites?

So I think this is the right thread to post a question regarding a humidifier. If I get a cheap one from say Wal-mart, will it help keep mites from appearing?? Also, what other benefits or problems would i be presenting to the environment?

If it gets to moist in the room or on plants or soil than mites are liable to appear, benefits you can control humidity better, downfall at times it can give you to much so you have to have the room constantly air out to let fresh air in