Since you are under 21, your best bet is to contact condo / cabin owners directly to see if they will rent to you. Very few hotels or motels will accept under 21 visitors.Rather than give you a specific property name and location, I would suggest that you do some research on the available houses/condos, the prices and the locations. I have used justvr.com in the past and it was quite helpful for narrowing down my choices and booking a few nights stay.
there are quite a few sites that you can search that will likely show you great hotels at the best prices available. check out the website BookMe and you will be able to compare prices on all the reputable travel sites in just a couple minutes. it s very convenient and will save you a bunch of time and money. Also, make sure you buy them online... otherwise they charge much higher fees for phone orders. good luck.