Dude...making money is difficult. Not hard, certainly not impossible...but YOU have to put effort into it. Spend the time looking for a better paying job. Buying/Selling merchandise online these days is best left to the pros. Selling a year or 18 month old phone on Craigslist is entirely different. Little to no risk and you can do it locally. Don't buy a new iPhone thinking you're gonna get rich. Others have outlined the facts, the math...and indisputable data has been given to ya---buy the phone and as you said...'Be Happy'. Sell it in a year or two. Recover your entry fee from this time around and buy the latest/greatest.
Money doesn't grow on trees. It's difficult to make, easy to spend. Your proposition is silly, especially considering you're a self admitted rookie. You're lookin' to get burned
J