Assume you are considering a studio. Keep in mind that the WDW
DVC resort studios have one queen bed and a double size sleep sofa plus a portable crip (Pac 'n Play). The OKW studios have two queen beds in them.
If you haven't already, go tto the Rent/Trade Forum and read all of the sticky threads at the top of the page. Feel free to ask specific questions here.
As far back as I can remember (late 90's), there has been only 1 report of a renter having problems. Owners are more likely to have problems with renters (and there haven't been many reports of that, either).
The most important thing is to completely understand the terms of the owner you choose to rent from before you send $$. Terms vary between owners. You can count on having a much more restrictive cancellation policy than you would if you went through CRO/WDWTC.
Since you can't book until March, you will almost surely be required to pay in advance - maybe as soon as the reservation is made. Most owners consider renting to be a non-refundable trransaction. Some will allow you to reschedule your trip, but that will depend on the status and epiration of the points used to make the reservation.
Availability is often limited 60 days or less from arrival. You may or may not have much choice of resort. However, May is one of the easier months to get a DVC reservation.
You will not get daily housekeeping when you rent from a DVC member. (Most members, including me, consider that a plus, though. I don't like worrying about scheduling my day around housekeeping.).
Renting can be an awesome deal for those who are willing to assume a bit of risk.
Best wishes -