I wouldn't buy lambs at 2 - 4 months... 2 months is too young and 4 month good lambs will be ready to kill and anything else will be poor stuff someone is trying to get shot of....!
Good stores are a tad older in my experience and are often the ones that are put away for the winter to be killed late winter early spring as lambs or a bit later as hogs! Stores are also very expensive at the moment!
Best profitable way to have a go and see if you actually like sheep is to buy a couple of older ewes with lambs at foot in April. They will eat your grass and you will get some experience of handling, shearing, worming, spraying etc. In the autumn pop the lambs in the freezer, keeping the skins to send for processing into lambskins. Send the ewes back to the market in the breeding ewe section and have a sheep free winter to contemplate the experience and decide if you like sheep or not...not everyone does!
Costs
To buy a ewe with 2 lambs around £110 - £120 plus depending on age type and breed 2 ewes with twin each = about £280max debit
To kill and butcher 4 lambs £25, value of sold meat if keeping a whole one for yourself 3 x £100 - £75 =£225 credit
Skins...£20 to abattoir to get them back so £20 each to process = £100 sell them for £50 each = £200 credit
Shearing £30 unless you do it yourself = £30 debit
Medicaments etc....some will last for following year £100 = £100 debit
Sale of ewes back at market in breeding ewes section £85 each if decent = £170 credit
Sundry items and unexpected stuff including transport if you have to borrow a trailer etc and market premiums £100 debit
Therefore Debits = £510 Credits = £595 plus a freezer with a lamb in it and the grass nicely mowed
Of course this is only ball park but is based on the prices around here in Somerset and based on buying some decent suffolk mule or other commercial type ewes with decent lambs at foot.....
Store lambs can range from £35 for total rubbish to £85 for good strong stores......