I believe the advice you've been given to purchase a second hand folding bike is good advice. Nothing can outweigh riding a bike before making a purchase. All the bikes I've rode before purchasing have turned out great. The few I purchased without a demo ride first have not worked out for me. As far as riding up hill if you're fit you can just stand out of the saddle for a bit and overcome most inclines. It's a lot more fun to stand on the pedals climbing and gives your body a change in position. There is nothing like riding a bike that fits and no amount of money that can overcome a poor fitting bike.