From memory of a relative becoming a barrister.
The fees for the Conversion course vary so City Uni charges approx. £13,590 in London but less £10,950 Exeter, Leeds etc.
The Bar Training Course fees range from approx. £12,640 to £20,220.
Not cheap but it is possible to get grants to cover these from the various Inns of Court. It is very competitive. If you have a first that's a good start. That's 2 years with no income or a low income at best.
You need to not just pass the courses but pass very well. So eg ideally an average of 80% in the Bar Course 12 exams (I think) will grade you 'Outstanding'.
You will need to volunteer at a law centre to get more experience while studying - maybe shadow a Judge etc.
You need to stand out from the crowd so maybe enter (and win) a law essay competition and / or a mooting competition.
You will have to do several mini pupillages in Chambers specialising in your chosen field where you will have the opportunity to see barristers at work.
I suggest you look up some of the Chambers near where you live and examine the qualifications and experience their pupils have. It will give you an idea of what the competition is that you are facing.
If you are one of the lucky few who get a pupillage offer, ( and you may have to apply for several years while working hopefully but in a lower law roll and still never get an offer ) Chambers will pay you varying amounts for the first six months when you shadow your trainer ie your Pupil Master ( used to be min. £12k I think ) and then usually guarantee you a similar minimum income when you are 'on your feet' earning money for the second six months. Some will pay you considerably more than this, £50K +.
You will have to have a lot of self belief for the Bar and a huge capacity for hard work, (lots of workaholics),a lot of travel to courts around your region requiring very early starts, excellent English and research skills and the ability to absorb stress. You are typically self employed (with irregular hours, last minute panics requiring sacrificing your weekends, working late into the night or very early mornings). No employee benefits whatsoever - no sick pay, no pension unless you arrange it yourself.
Earns well over £150k pa 13 years call ( not in commercial law where earnings are much higher or criminal ( often much lower)
(There are some employed posts though ie in the Civil Service or Solicitor firms maybe.)