If you are thinking about keeping a few sheep for milking, you are probably also wondering how many you should keep. While making this decision, you will have to take a few factors into consideration: How much space you have: If you have little space, then you will only be able to keep a few sheep. Stocking rates for sheep can be anywhere from 2 to 6 animals per acre, year round. The number of sheep you can keep on an acre depends on the quality of the forage. This number can be higher if you plan to supplement a lot of hay but that method is usually less cost effective. If you are just getting started with sheep and have at least an acre of pasture for them, then you would be safe starting with 2 or 3 sheep.
How much time you have: Of course the more time you have to spend with your flock, the more sheep you may have. Sheep are pretty low maintenance especially when kept using an extensive model with free-choice pasture year round but you have to consider how much time it will take to milk each sheep as well. Hand milking will take longer than machine milking and your small-scale milking machine will take longer to milk a few sheep than it would take a larger scale operation to make 10 or 20, just because of the differences in operation and set-up. You also have to consider time spend tending to the lambs if needed and maintenance on your sheep like hoof trimming, vaccinations and shearing if you have wool breeds.
How much milk you want: Before starting your dairy sheep venture, you should determine how much milk you go through in a week. This a great starting point to determine what your dairy needs will be and which breeds you need to keep. For example, my experience with milking katahdin sheep is that 2 ewes will produce at least 1 gallon per week but it can be up to 2 gallons per week. A third katahdin ewe would guarantee I had 2 gallons of sheep milk per week. 3 gallons of sheep milk would be enough for one to drink a gallon a week and use the other two gallons to make a 6" diameter wheel of pecorino romano. If you want to delve into what a dairy breed might produce, you could expect between 1 to 2 gallons of sheep milk per ewe from something like an east friesian.
Which dairy products you intend to produce: If you all want is milk and you have a small family, then you can certainly get by with only a few ewes, depending on the breed. However, if you are looking to make cheese, then you are going to be going through a lot more milk than if you were just drinking it. So you may want to consider keeping more sheep or only keeping dairy breeds of sheep.
As with most new things, one should always start slow and small because it can be easy to get overwhelmed. If the ewes don't meet your needs the first year then it is easy to scale up in following years. But if you start too big the first year, it make discourage you from continuing your venture in milking sheep and that would be a loss.