We registered this great domain in year-2004 making name well-aged and giving extra value. There are more than 30,000,000 results in Google on a "fsbo" search.
Some popular related searches are about; FSBO - For Sale By Owner, HUD foreclosure listings, sell by owner websites, sell by owner, houses for sale by owner, FSBO listings, FSBO real estate, best sale by owner websites, videos of FSBO, free FSBO listings.
FSBO.us is available and on-sale due to its owner retiring soon. In fact, a desire for retirement income is a reason the owner can do an interest-free monthly payment plan (and a buyer's benefit).
P.S. No worries about using the domain while paying. You will have the same use as if you paid purchase price up-front, and be able to use your own DNS immediately upon making your first payment.