Check with your local zoning to determine if you are allowed to have chickens. For example where I live (suburb) you can have 5 chickens total but no roosters.
Here is an excellent article to build an affordable, portable and predator-proof chicken coop: http://www.motherearthnews.com/do-it-yourself/how-to-build-a-chicken-coop-zm0z11zhun.aspx
Green Real Estate Appraiser 