DVC Rentals:
You need to plan in advance (its WAY too late to get the Boardwalk area for this March). Preferably eleven months out.
Reservations are usually final - you get pregnant, that's your problem. You lose your job, that's your problem. A hurricane rolls in, that's your problem - get insurance.
If the owner behind your points doesn't pay their dues or goes into foreclosure, your reservation will be cancelled - if you go through a broker, you will get your money back, but won't have a room.
DVC studios are (with the exception of OKW) a queen bed and a pull out couch. Many studios have a pull down smallish twin to sleep a fifth person. You don't get two "real beds."
DVC checking time is AFTER 4 and there is no late checkout - its 11am.
You will not be eligible for specials (like free dining) that come along. And remember, you can't cancel your reservation if free dining is released for your dates. Every year we see angry renters who can't get free dining and can't cancel their DVC rental.
There is no daily housekeeping - or daily towel refresh. If you need clean towels every day - you may end up paying for them (sometimes they don't charge, but by contract, they can).
Generally, you pay upfront.
There are more people interesting in renting DVC points - especially at the near park resorts - than there are owners interested in renting out their points. Just because you've decided to rent points does not mean you will find an owner who has point to rent you.
DVC units are well used between refreshes with high occupancy rates. Expect broken drawer pulls or scuffs on walls or stained carpet - that's pretty normal. Member dues pay for refreshes, and members mostly don't want to pay for perfection.
Disney is not involved in rentals of DVC units - if something goes wrong, they aren't going to make magic happen. It is a private arrangement between two individuals. There may be a broker involved - but they are just matchmaking and holding money in escrow to add security. They have no control over an owner defaulting on their loan.
Some of this might be different with different private owners - some private owners would let you sublet a reservation you can't use. Others won't (because their contract is with you and the member is responsible for their "guests." ). Some will let you pay half upfront and half sixty days out or something. Some will try and move your reservation if needed. Others won't. Brokers generally won't even talk to you about it.