Seeking for Scrum certification- but not from IT industry

1) if one is not from IT background and doing the scrum certification- how easy it is to get the scrum master job?

It depends on what other skills you have. You don't necessarily need a strong IT or software development background to be successful. What other agile and lean methods and frameworks are you familiar with? Can you facilitate meetings and events? Can you provide teaching or mentoring of a relevant subject? Since you don't have a technical background, do you have experience in product management or organizational change? You may not need to hit all these points, but these cover the breadth of the skills needed by a Scrum Master, so they represent things that you should be continuing to learn and develop.

2) How a scrum master would understand / estimate the time box for each sprint when scrum master is not very much aware of how long the work will take to delivery values in user stories?

The Scrum Master does not need to estimate the time box for each Sprint. Generally, Sprint lengths are fixed for an extended period. The team may discuss changing the length at a Sprint Retrospective, but it's not something that should be done frequently. In my experience, the biggest contributing factor to Sprint length is how long between synchronizing with key external stakeholders or how long you want to wait between Sprint Reviews. You would want to consider the time and availability of the key stakeholders to support high quality Sprint Reviews along with the uncertainty of the environment. The more uncertain the context, the more frequent you would want to have a Sprint Review, but you also want to make sure that it's not too frequent to burden your stakeholders. Once you have the Sprint length, the team can work to refine and define the work into changes that can be delivered within the Sprint timebox.

1) Getting a Scrum Certification does not guarantee you will be able to get a job as a Scrum Master.  At least not in the part of the United States where I live/work. Proving that you understand the framework, how it can provide benefits, that you are capable as a servant-leader is what can get you a job as a Scrum Master.

2) If you have studied the Scrum framework as it is explained in the official Scrum Guide, you would know that a Scrum Master does not estimate time boxes for each Sprint.  It is up to the entire Scrum Team to decide on a cadence that makes it possible for them to consistently deliver valuable increments of product changes. This is usually done through experimentation of varying time boxes. Once the "right" timebox is found, the timebox usually remains the same for all following Sprints. Scrum Masters actually do not need to understand the technology that is in use.  Their responsibility is to help the Scrum Team and the larger organization to understand the Scrum framework, appreciating the empirical nature of the framework, and how best to interact in an empirical manner in order to receive the benefits. 

I must say this course and overall methodology is very interesting and easy to understand. 

If you believe that Scrum is a methodology, then I question the validity of the "course" you are using.  These are the 5th and 6th sentences in the official Scrum Guide.

The Scrum Guide contains the definition of Scrum. Each element of the framework serves a specific purpose that is essential to the overall value and results realized with Scrum. 

Notice that it points out that Scrum is a framework. The word "methodology" is not used in the Guide at all. The word "methodologies" is present once, in the end note of the Guide.

Scrum is free and offered in this Guide. The Scrum framework, as outlined herein, is immutable. While implementing only parts of Scrum is possible, the result is not Scrum. Scrum exists only in its entirety and functions well as a container for other techniques, methodologies, and practices.

You did not mention what "course" you were using but if it says that Scrum is a methodology, then I don't think it is a very good one.

1) if one is not from IT background and doing the scrum certification- how easy it is to get the scrum master job?

It isn't a job, it's an accountability. Once you hold yourself accountable for people's understanding of Scrum and the effectiveness of its implementation, you are a Scrum Master.

2) How a scrum master would understand / estimate the time box for each sprint when scrum master is not very much aware of how long the work will take to delivery values in user stories?

You wouldn't. The business context would. There will be an optimal rate for which value can be delivered, lessons learned, and empirical process control established and maintained. The best thing to do is to manage people's understanding of this so they can then self-manage their time-boxed work more effectively.

Thank you @Tomas Owens @Daniel Wilhite @Ian Mitchell for your valuable insights. 

I come from Hospitality background and i have just started preparing for professional scrum master course. 

For me total framework and concept is new but i have been working in management role from past 9 years so people, time management is one of my strengths. 

Thank you once again 

Let try to put this in terms of the hospitality industry. It is going to be very simplified and probably not completely accurate but i think the story will play out. 

In the hotel business, you will have different teams of people to do work.  Let's take the housekeeping department for example.  In that department there are teams of people that clean the rooms every day. There are teams of people that clean linens. There are teams of people that make repairs to rooms.  Communication across those three category of teams is important. 

• If the Linen teams does not clean enough linens or has an equipment breakdown, the Cleaning team will need to know so that they can adjust the work that they will be doing.
• The Cleaning team is the only team that enters rooms every day so they need to communicate any repairs that need to be done to the Repair team. 
• If the Cleaning team does not retrieve the dirty linens from rooms and deliver them to the Linen team on a timely basis, the Cleaning team will not be able to clean the linens in time for them to be used again.

Each of these teams could be considered a Scrum Team.  There are:

• people that do the actual work (Developers),
• someone that orders the work that needs to be done to ensure the people doing the work are focused on the right things (Product Owner), and
• someone that makes sure the people doing work have all the things they need to do their work (Scrum Master).  The Scrum Master also helps to educate the other teams in the housekeeping department and those in other departments on how to best communicate with the team they are part of and to understand how the team operates.

Notice that no one in the group is "in charge".  Everyone has a role in making the team successful.  If one of the roles is not fulfilled, the team will have difficulty in succeeding.

Scrum is a framework that provides some guidance on events, roles, boundaries that can help teams be more productive at delivering value.  The actual methods (methodology) that are used by each team is not defined by Scrum.  Those are up to the team to determine and implement. The focus of Scrum is not on how many hours everyone works, but on the continuous incremental delivery of value. 

Hope this helps a little bit and doesn't make it more confusing.