Don't pay Apple to upgrade the RAM. You can (or could) get 8gb for around $40 a few months back, and I have my 8gb I'm willing to sell for less than that. I paid $160 to Newegg for the 16gb, so there's a huge price difference to go up to 16gb. You could do that later on if you find that's something you want. But I would upgrade to 8gb asap and you can sell your old 4gb on eBay and get some of that money back. I think I sold my original 4gb for just over $20 on eBay.
Never fear, I'm not paying apple! I won't have 4 to sell because I'm just getting the base one. "Poor-starving-student-single-mom-of-three" here, my fellow classmates are springing for the $350 laptops at staples. Yuck. Luckily my kids like beans and are excited about a new Mac! Lol! (disclaimer, I'm joking about having to feed them beans to buy it- but they would be happy having burritos every night! But my ex will copy this to use in court, so I'm not neglecting my kids for a computer)