30/700 = 42/1000 = 4,2%

You don't need to be particularly fit, especially if you make sure the bike has low gears (eg. 2m/25"). At worst, during the first few weeks, you can always walk that part.

Since you're not sure you'll stick to riding, get a second hand bike that you can easily resell, so you don't lost any/much money in the process.

I recommend you get one that has a welded lug in the front — most Dahon's have one, but not all — so you can carry a bag on the frame and avoid backpacks, and preferabley with a gear hub instead of a derailleur so you can change gears any time.