Hello
Firstly, if you bought your pigs as fatteners are they suitable for breeding? Have they got at least 12 evenly spaced teats, better still fourteen. And no dummies. To be fair to the breeder he sold you pigs for fattening not for breeding, which would have been more expensive.
Secondly, have you got an outlet for all those potential weaners or pork?
Thirdly, have you worked out the cost of keeping a sow, feeding a sow and piglets etc. and are you happy you can break even for a start?
I don't want to put you off but if you don't have an outlet think very seriously about breeding pigs. I'm not saying it isn't possible to make money out of pigs but it can be hard and many people get out of their depth very quickly.
In terms of arks buy the best you can afford. Get proper farrowing arks with rails. Personally, I would go with your empty stables for now.