It depends what you want to do-
1. Manager- you are employed by a brewery, earn a wage+bonus, & there is no outlay by you.
2. Tenent- you buy the contents of the pub, the brewery owns the building, you pay the brewery a rent & have to buy your stock from the brewery, but the takings are yours.
3. Freehold- you buy a pub, own it, and do with it what you please.
If its one of the first two, try looking on one of the big brewerys web sites ie www.greeneking.co.uk/run_your_own_pub.htm. If its the third you are obviously loaded,