Just for example, here are two viable schemes for breeding on your 4 acres.
1. Buy Mule ewes and produce fat and store lambs.
You say there are mules in the area. A Mule to a Texel type commercial tup will produce good fat lambs, many of whom will fatten before their first winter. So you could have a flock of say 6 mule ewes, tup them for approx 12 lambs between them, and sell all 12 lambs (fat or store according to how they do) in or by October. 18 mouths in summer - no problem on your good ground, and just the 6 ewes to overwinter, so no probs on your 4 acres with that. You could even hold a few of the smaller lambs back to fatten and sell after New Year.
2. Plump for a small breed, eg Shetlands, and produce meat.
(What you would struggle to do on your 4 acres is produce the numbers you would need in order to build a reputation as a producer of pedigree breeding sheep. So if you do decide to choose a breed and breed pure, it would be for pleasure and meat.)
4 breeding ewes to produce approx 7 lambs each year. Some of the lambs may be ready by end October, but many will need to overwinter and fitten in spring, so you would either be carrying some hoggs through winter, or would have to find an outlet for store lambs. If there are other smallholders about, the latter may be easy to do, but they won't be of interest to "proper" farmers.
It's a guess without seeing the land but I would anticipate that 4 acres of southern land would happily manage something like 4 primitive ewes and 4 overwintering hoggs, with a peak population after lambing of 20 (4 ewes. 4 fittening hoggs and the 7 or 8 new lambs.) If you find an outlet for your store lambs, you could go up to say 8 ewes, as you would have only them over winter, and 4 acres which hasn't been trashed over winter should easily feed 8 small ewes with their 14-16 lambs in summer.