Is the Abandoned Shack usable as a safehouse?

I'm talking of the one located outside Goodsprings, near the big cross memorial.

Everything is usable as long as you can travel to it directly from the world map and there are no deathclaws inside. But I like having an own bed in the hotel in Novac instead of dumping my stuff somewhere in a place called "shack".

Hehe, me too.

I'm playing a new game from hardcoe mode, though, and I take my time. I practically stay encumbered, so having a place to stay, temporary though it may be, is nice before I get to Novac.

Good Springs Wells has a few beds for you, always fresh water and I think a few crates too to store what you don't need (I don't think loot disappears but you want to put stuff inside, travel to Vegas, save, restart the game, go back to the game, wait 73h, save, quit, restart and go back to make SURE they don't vanish). You can cook there, Geckos spawn every third day for meat source.

It's a sweet sweet place. hardcoe is fun as long as you can stick around it going back for night to cook, drink, sleep and then resume questing.

Looking through GECK, neither of the two containers in there is set to respawn so you should be OK.