I'd add to the above advice that you look at the gearing of the bike you wish to buy if you're looking at lots of climbing. You might be served better if your largest rear cog has more teeth than your smallest front chainring, making it easier to ride the bike up the hill (with lots of pedaling) to avoid stalling out, until your fitness improves (which it will do quickly). Just search for your favorite bike gear calculator on google, and see what you come up with. It's much simpler to replace cassettes (the rear cogs) than the chainrings.