Unlocked phones means the phone can be used with any carrier. Keep in mind you may not be able to use all of the phones features.
NewEgg is the highest rated store by customers that sells unlocked phones. Amazon also has high reviews but only slightly less. The thing with Amazon is some people sell through the site rather than you buying directly from Amazon so it's similar to Ebay in regards to phones.
Do you mean unblocked, as in not filtered at school? https://sites.google.com/site/newstudyhall/
No. Straight Talk has a SIM program where they accept unlocked phones from other carriers to join as a customers, though the phones they accept are limited to unlocked GSM phones and T-Mobile compatible phones.
Ebay has a lot of phones on sale. you can either bid on the one you want or buy one instantly. Just be sure to know what you are looking for before you go to the site and make sure the seller is eBay verified!
If you are talking about the iPhone, then no. The unlocked iPhone will ONLY be able to run on GSM networks, such as AT&T, in the US. It will not run on CDMA craaiers, such as Verizon or Sprint. This goes for all 3 2012 current iPhone models: iPohne 3GS, iPhone 4, and iPhone 4S. It may also apply to other phones ( e.g. the nexus line of phones, and the htc one S/X
Never trust a website that gives out free stuff.
This is a complicated question. I'm going to link you to a site that explains it in more depth that I can. http://www.engadget.com/2007/08/24/know-your-rights-is-it-illegal-to-unlock-my-iphone/
From my search I couldn't find a book that teaches cell phones for seniors. I did however find a site that offers senior friendly phones. The site is www.info4cellphones.com/cell-phones-for-seniors.html.
Cellhut.com is the best online shopping site, you can get unlocked cellphones with huge discounts. i bought Blackberry Curve 8520 Red unlocked from them. Shipping is Also free.
I found a site that list the top 5 cell phones , so I would tell you to check this site out reviews.cnet.com/best-cell-phones . Or here is another site that list the best cell phones towww.brighthand.com/price it also includes the prices for the cell phones which is great.
eBay
You can find these phones by going to the actual website. There you will find that there are many that are offered on the site. There are many nice phones such as smart phones.