If it is your first time it is going to take much, much longer. If the only way to learn is on the job then you must have an experienced plumber by your side, otherwise you're going to bill 4 hours for a 1 hour job because you are not fast enough. Your first year is going to suck or you only ever do the same few skills you have learned by taking a risk. A botched job may have a much higher impact than a bug in a CRUD app (there are always exceptions).
That's a lot of nines.
It means if you were doing 5 of these tasks a day, for 250 working days a year, you'd expect only a 50% chance of finding a task too curly to do easily in the first 550 years of your working life.
I feel like there's very few people, in any field, who've earned that level of confidence.
A professional tradesmen _knows_ he can show up to your home/business and fix your problem(s) with 99.999% certainty.