Make sure you buy from someone who is knowledgeable. Other times they will offer tons of advice, listen closely and see if you can incorporate any of these ideas into your own lifestyle and usage. It's apparent this agent is not concerned with you. A thoughtful representative will suggest several phones, but allow you to decide what phone is right for you. Remember if you do not like the phone you choose, you will be less inclined to actually use it.
Most places also have strict return policy on used phones, so buyer beware.
Most people settle for a lower grade or cheaper phone because they can't afford or don't want to spend the extra money for the one they want. This isn't a major problem but you must keep in mind that you will have this phone for at least one year. And if you decide to upgrade later on it WILL cost you more. So if you can afford the phone you want, buy it, you'll thank yourself later on. On the flip side, don't over buy.