Don’t use Vélib to go to areas with a popular bar culture. I spent 50 minutes cycling round the Ledru Rollin area looking for a spare borne and had to park miles from the bar my friends were waiting in.
Also don’t count on finding one near your home after 2am (bar closing time). You may end up having to leave it locked to a gatepost all night, which would incur a cost of about €70 (it’s €4 the half hour after the first half hour). It’s Russian roulette with your credit card.
My advice is to try Vélib to see if you think cycling in Paris is for you, then buy a second hand bike, bash it up a (…)