I have done the design and licencing for bars and resturants and yup it is a mightmare. depending on your plans 3 or 4 different licences are needed, special conditions meet ie fire doors, ventilation, sprinklers, sewerage, toilets, etc.
Whatever you do - don't DONT pay any money, deposit or agree to lease any space until someone has checked the space. Of course ignore the nonsense from property agents.
rules change over the years, get tighter every year, so dont assume that a former bar will comply with latest regulations.
many bars fail, seen many close over the years. If you want to learn more feel free to ask.
Rent is expensive, ask an agent for viewing to get idea of opening "asking" rent and make a bid lower. Renting from the major landloards, Cheung Kong, Wheelock, etc. is much harder than from Joe blogs.