If you are like a lot of New Yorkers, you may have trouble finding a safe and dry place to put your bike at home. Your tiny apartment refuses to budge another inch, and the street seems to be the place bikes get left to find new owners. You may also want to ride to work, but parking is hard to find. If you try to take your bike into your building, the concierge looks at your bike as if it was a giant wheeled rat and refuses to let you onto the elevator. You may also long to take your bike along on a trip that requires transit, but cannot because of rush hour restrictions or outright bans on bicycles on trains or buses. The solution you are looking for might be a folding bike.
Folding bikes can be taken with you right into your apartment, onto elevators, and into your office. This works particularly well if you also cover your bike so that no one has the chance to register "bike" and react to it.
Folding bikes also only rarely suffer the indignity of being stolen, because for the most part, the bike does not leave your sight. No more of that anticipation and dread as you walk back to your street-parked bike: "Will it still be there today?" There is also no need to carry a heavy NYC-proof lock with you while riding.
Throw away your assumptions about rickety, heavy folding bicycles that are hard to fold, fall apart while you are riding, perform badly, give you a bad ride, or require a lot of pedaling. There are now many good quality makes and models to choose from that alternately optimize ease of folding and folding size, performance, ride, and price.
Common to almost all models is that the handling is more responsive than on a full-size bike, and that can take some getting used to. It is not advised that you ride a folding bike with no hands or try any cute stunts. Gears on small-wheeled folding bikes are higher to compensate, but limited gearing on some models may slow you down. If that is a major concern for you, you might want to look more toward higher end "performance" folding bikes. If you plan to take a lot of trips that utilize transit, a bike that folds quickly and compactly may be best for you. If you are a tall rider, you may want to check out how each type of folding bike can adjust to fit you.
As with any purchase, ask yourself how you plan to use the bike and try to find the one that matches your needs best. Remember that you often get what you pay for and that a lower-quality bike may make you wish you had bought a better bike in the first place. The better quality folding bikes may seem expensive, but considering that a typical non-folding bike takes up 20 square feet in an apartment, you'll save perhaps $10,000 over ten years by being able to get a slightly smaller apartment. So you can't afford not to buy a good-quality folding bike.
Be aware that folding bikes are not for the shy. You will be asked about your bike constantly on the streets of New York, so get ready to be a spokesperson for whatever bike you choose. Folding bikes are apparently the most thrilling sight many New Yorkers have ever seen!