Greywyn Deepscorn......

[DeadBread]

Seems an awfully resourceful vampire. He manages to discover a cure for vampirism in about 13 days since he first started searching for a cure. Quite impressive in comparision to, say, Vicente Valtieri, who has been a vampire for over 300 years, spent 200 of those with the Dark Brotherhood and thinks that Raminus Polus might know a cure (Not to mention the quest)!

Either that, or it's a huge retcon of sorts to give players a very easy way to cure vampirism.

[I_am_one]

And the fact he managed to build an underground/under water lair. I can imagine that's not an easy task.

[DerangedPickle]

Does it mention how old he was? Or if he had help, because 100 years isn't long for a Vampire, also considering the power he'd get from vampirism, don't get me wrong it would still take a very, very long time.

[KrisCrash]

Quite frankly, I didn't find the "house mod" DLCs to have that good of a story to them. They're more like overpowered player goodies.
So you want to have a gloomy dark brotherhood / vampire abode? Ok. Don't want to have to bother with curing vampirism? Ok, here it is.
So you want to make spells and not be in the mages' guild? Easy. Etc.

[DeadBread]

Quite frankly, I didn't find the "house mod" DLCs to have that good of a story to them. They're more like overpowered player goodies.
So you want to have a gloomy dark brotherhood / vampire abode? Ok. Don't want to have to bother with curing vampirism? Ok, here it is.
So you want to make spells and not be in the mages' guild? Easy. Etc.

I actually agree with you on all points, I was just commenting on the information provided in the book at the entrance to the hollow.

But I would play devil's advocate and say that upgrading the houses is quite costly if you're starting a new character. Upgrading, for example, Frostcrag spire, at level 1 with low mercantile costs about 6K total, not something you could easily cough up. While to do the same thing in the Arcane University would require you to do about 1 hour to 1 and a half hours work going and completing all the mages guild's recommendations.

[Jeff]

Not that costly, as it comes with it's own cache, 4 actually:

Spoiler:

Scattered around Deepscorn are Greywyn's Jewelry Caches containing a large amount of leveled miscellaneous jewelry, gems and gold. These are available as soon as you enter Deepscorn Hollow (no upgrades need to be purchased)

Greywyn's First Cache is located in the left hand side corner of the first room you enter (behind the garden).
Greywyn's Second Cache rests beside the Font of Renewal under the water.
Greywyn's Third Cache is located in the corner of the Cattle Cage that holds the feeding body near the Cell Door. (If you have not yet purchased the Cattle Cage upgrade, this location is in the cave-like room on the west side of Deepscorn Cloister, hidden against the wall south of the entryway).
Greywyn's Final Cache is behind a glowing blue rock on the left side of the Shrine to Sithis area. This one cache will contain a random, leveled enchanted ring or necklace.
High above the first room (where the Garden of Venomgrowth is eventually placed) there is a bucket filled with gold. If you shoot it, the gold will fall to the ground. This is mostly for the novelty value of seeing all the gold come out, because you will have to pick each piece up individually.

Any gold you do not pick up will respawn on the bucket after three days, meaning you can shoot it again and again and pick up any hard-to-find coins.

[Elune]

The stuff in Greywyns Caches really isn't worth that much, literally the only exception being the one enchanted item. Everything else is really low tier stuff.