AFAIK, in contract law, an "accepted offer" is an actual contract, even if there's no paper record of it (though it may be a bit hard to prove acceptance without one). However, when someone puts their house up for sale, they're usually not offering it to anyone yet, rather they're inviting others to offer to buy it.
I think a term sheet is also just an invitation, not a binding offer.
I think a term sheet is also just an invitation, not a binding offer.