Too much of one.
A bunch of hungry refugees flooding the place is going to hurt.
I don't think there's enough to get this off the ground, really.
OK, let's try to refine things a bit.
The POD could be some random shipload of Europeans get washed up ashore in North America a short while before the Vinland expedition. The locals would be unlucky enough to pick up some epidemic diseases from that first boatload which takes a severe bite out of their population numbers before Erik the Red gets to Vinland. This die-off results in a boom in the deer population and coastal fish/shellfish stocks.
Then, thanks to butterflies and a slice of good luck, Erik the Red lands somewhere with a lot of easy to gather coastal shellfish and where the die-off of the locals has been especially severe. That should keep them alive side gathering coastal shellfish is pretty idiot-proof as a way of providing food, provides food for a lot of people in a small area (until the stocks start getting depleted) and isn't vulnerable to attack (enemies can't burn your fields or steal your livestock).
So the coastal shellfish (and fishing and hunting the burgeoning deer population) keeps the *Vinlanders alive with perhaps a bit of farming on the side. Eventually they get the hang of farming that works well in the *Vinland climate but that might take a while. Sheep herding would probably work well as well in the middle-term.
Also once the coastal shellfish stocks start getting depleted the *Vinlanders could start sailing out and fishing for cod. Cod would exist in pretty massive numbers off the coast (and not too far off the coast, at least to start with, although eventually they'd have to sail farther afield to the Grand Banks etc.) and cod are pretty damn easy to catch.
While dried cod isn't that best trade good in the world, the amount of protein per pound you get if you dry it down is pretty awesome and Iceland is often hungry so that's at least something.
That might keep the people fed long enough to get them over the initial hump. Once they're established they can make some money selling furs which might catch on in Europe as IOTL which'd bring more immigration over later. For early immigration, they'd be able to get at least a trickle from Iceland since Scandinavian farming practices lead to a lot of erosion of the fragile Icelandic soil so after the initial colonization of Iceland the yields they were able to get from farming and herding fell off so if Vinland gets established with even a few hundred people they could probably attract at least a small amount per year due to Iceland being a pretty hungry place. Also the *Vinlanders could raid the locals and take kids as thralls to boost their numbers. They might be able to get away with that if we kick the poor locals in the gut hard enough with disease to make it hard for them to fight back effectively, especially if we stick the *Vinlanders in islands off the coast, perhaps PEI or coastal Maine or Martha's Vinyard or something.
