system
Given the following post, respond as if you're commenting on Reddit:
human
[VtM] What is the smallest herd a Vampire could live off without killing them?

Under Vampire: The Masquerade rules, a Kindred must expend one blood point (defined as a pint or half a liter, iirc, feel free to correct me if that's wrong) to awaken every night, and further points to use his/her vampiric powers (Usually 1 point per use). Vampires in this setting can also feed without killing their victims, and it's fairly common for them to keep 'herds' of mortals to sate their apatite, feeding from a different member each night so as not to drain any of them.

So, I propose three scenarios:

1. A vampire who never uses his/her disciplines or powers, only wakes up each evening, expending one blood point to do so.

2. A vampire who does make use of his/her powers in addition to waking each evening, spending, on average, an additional 2 BP per night.

3. A vampire who, in addition to waking up and using his/her powers, keeps a ghoul. Ghouls are humans who drink vampire blood. It keeps them from aging, gives them limited use of vampiric powers, and makes them utterly devoted to the vampire who feeds them. Let's say our hypothetical vamp feeds his ghoul once a week, meaning that s/he expends a total of 22 BP in an average week.

What is the smallest herd of mortals this Kindred could maintain in each of these scenarios, without killing them, and feeding exclusively from them?

EDIT: I checked it V20. I was right. A blood point is half a liter, or approximately "One tenth of the blood in an average adult mortal."
gpt
A safe ballpark figure for "humans" is about 5000ml of blood total. After a single point loss of around 2000ml you're looking at life threateningly low pressure and will generally be incapable of doing much of anything for yourself. A healthy adult human with plenty can sustain 500ish ml of replenishment of all the various components that go into blood per week. This figure can vary pretty wildly and can be as low as 300 or as high as 800 from some cursory googling.

So if you're willing to kill them and hang them upside down for all that red goodness, a human is worth 10BP. 
If you're willing to risk killing them but otherwise don't need them to do anything but lay there and survive, a human is worth 4BP.
The average healthy human replenishes 1 BP a week, assuming each BP represents about half a liter of whole, complete blood including all the plasma, red cells, etc. 

* Scenario 1 requires seven thralls. (One each day)

* Scenario 2 requires twenty one. (Three each day)

* Scenario 3 requires.. well.. twenty two. (Specified as 22BP per week).

In any case this represents the bare minimum figures. It would be wise to add a percentage of replacements and backups. People have accidents and become ill. A single Kindred that did not particularly care to exert him or herself could probably make due with a steady flock of about thirty people, maybe less if they expend some of their powers in pursuit of keeping everybody safe.