It's a big step change from keeping a few weaners to breeding, mainly because if it goes wrong you could lose all the piglets and the sow. Furthermore, if you don't have an outlet for the piglets you could be left with a lot of hungry mouths to feed, which is expensive, they are then all ready for slaughter at the same time so you end up with a mountain of pork to try and sell.
We all end up with piglets that don't sell, you could sell them cheap but you are then giving any profit to someone else, so you really need to understand the market, preferably with pre-arranged buyers, then keep the runts (you will get them) for your own freezer.
You would be better off finding a local breeder and chatting it through with them, they will give you a good idea of how hard it can be raising weaners, and also how satisfying, along with all the pitfalls they found as they developed their breeding system.
Experience counts for everything, the more you have the more likely you are to succeed, enjoy keeping weaners and help out somewhere that breeds, you will then be in a better position to decide if you want to take the plunge.
Good luck