OK, after spending much time on this, I figured out how you could get it.
I wasn't planning on joining the stormcloaks, but that is what I did so I could turn Falkreath over to them and change the Jarl since Siddgeir was being a loser. The new Jarl, or should I say "old" Jarl, has a different steward named Tekla. She will offer you the property.
There you go. I am not too happy about having to join the cloaks since I hate Ulfric, but it appears to be the only way to get the house if Helvard is dead. Hope this solves any other problems people might have in this spot.
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I had the same issue since Helvard was dead, but I talked to the Jarl (young punk) and brought him a Black-Briar Mead like he wanted, then he offered me the Thane thang, with the stipulation of owning property. I was then able to buy the land from the steward.