If the house was willed to Sookie and in her name alone then realistically I find it pretty unbelievable that Jason was able to sell the house with in a year (since as you said there is no body). However if they never changed the name on the house (which is also not unheard of here) then technically he could claim the grandmother had died and there was a body and sell it out from under Sookie (but again the paperwork involved in that would likely take much more than a year) and it would again involve some degree of probate.
Either way what plot point does selling the house serve. I always liked that she owned the house in the book. I won't be watching this until next year when it comes out on DVD and will likely have the same question then as well. Basically what was the point of it in the story of the show?