A live band, playing in a pub.
A most risky tactic for the pub.
It is a gamble: That you will have increased custom to pay for the band, and then some.
It is a one-off gamble. That is, there is no residual effect, as there would be from say new furniture. You are paying a lot for live music, and can only use that music while it hangs in the air. As soon as it is gone, so is any benefit.
Tomorrow night, or next week, you'll have to think up something new all over again (perhaps a different band - but who knows how it'll turn out?)
Most likely it will pan out so:
First off you will require smelling salts. This will be of invaluable assistance for coping when you learn the band's fee.
The band will have a list of demands for extras on top of the stiff fee (no band plays for less than $1000 per night, booked for a minimum of two nights. Well, last time I used one anyway)
(a) They will want "free drinks all night" for the band & also for their groupies. Answer: NO
(b) They will want overnight accommodation for all the band. You don't have much choice in this. Usually they'll sleep almost anywhere, however if you don't have space you'll have to use motel rooms, and that gets expensive!
(c) They will want free meals for all band members.
At gig time the band will start off with dirges, that steadily empty the pub. People will slowly stream out.
The band will knock off for regular breaks of up to 3/4 of an hour. During this time the pub will continue to empty.
If you are lucky, or have made an astute choice of band, they will be playing the sort of music that "works" in your pub.
By the end of the gig the band will have warmed up and be playing livlier stuff, that had they played this to start with, the pub would now be full of people.
With very few exceptions this is how your live band experience will be.
It mostly won't be worth the effort.