Anywhere between a year to..... NEVER
You are going to a flight school without getting the facts first. Look around these boards a little longer and then make a decision whether you want to get yourself into this mess.

 

They say timing is everything... In this business it's more true than ever!!! When you get hired and how many colleagues you stack below you on the seniroity list determines pretty much your entire life, commute, pay, advancement and above all: Quality of Life!

Start over somewhere else regardless of reason (furlough, own decision etc.) and you're back at the bottom working your way up from the lowest pay, the crappiest schedule, reserve (again) and QoL. The same holds true for upgrades. Your schedule almost certainly degrades, fewer days off, and worse QoL - but better pay. Reason why is because you will likely not be as senior as a fresh CA as you were as a FO just before upgrading.

There's the saying: "Life will never be as good again as when you were a senior FO" (aside from pay of course), and that explains why many pilots, especially at the majors hold out on upgrading aside from the company not running classes...

Good luck. Think long and hard about where you want to go and pray that your timing is right!!!

 

It's good that you are asking questions but the questions that you are asking show that you still have some research to do!

FO - CA Upgrade: There are many variables between companies, including growth (or downsizing) and demographics of the pilot population.

If a major has a lot of old pilots, there will be many retirements soon (and vice versa).

At a regional, movement usually occurs due to CA's taking jobs at major airlines...but if the regional is a good place to work, or majors are not hiring, upgrades can take a long time.

These numbers are probably a good average...

Regional: 3 months - 12 years (2-4 years typical)
Major: 3 Years - Never (7-15 years typical)

 

By reading your post, I get the idea that you are a young man, probably in your late teens. I would like to offer this advice. Don`t plan for a career as an air line pilot. I spent 30 years in that profession, my son is an air line pilot also. This career will be a disapointment for you. Youy will work for years for slave wages, probably be furloughed a couple of times and more than likely spend a lot of days commuting to and from your job. Do something else, and fly a Cessna for pleasure on the weekends.

 

Do what you want. I love my job. I wouldn't do anything else. Listen to everyone's advice and make up your own mind. If you want to be an airline pilot after learning about the job, then do it. It beats working 9-5 in a cubicle.