How easy is it to find month-to-month leases in Houston, TX?

[Bryan T.]

How easy is it to find month-to-month leases in Houston, TX? I am planning to rent either a private room or an entire apartment in Houston. I am wondering what % of landlords would be willing to do month-to-month leases for either a private room or an entire apartment? 

Is there a general % across U.S. that are willing to do month-to-month? A lot of the websites (e.g. apartments.com) say year-long lease but can I negotiate and ask for month-to-month? Are most landlords willing to do month-to-month, 3-months or 6 months?