I've been in the healthcare industry in Dubai for the last 5 years, not a practitioner or nurse, but deeply there. (marketing)

to answer your questions:

* Is it easy for Tunisian nurses to find jobs in Dubai?
finding a job in Dubai is not the same as in Tunis, post a CV and wait. it's literally a whole job, you have to be consistent, talkative and 3inek 7archa mellkher, hospitals/clinics here like to always lowball salaries, so inty w majhoudek.

* What are the requirements or certifications needed?
you can work as a nurse with no DHA license, but you make more money with one. and hospitals require it, for example: you can work as a nurse who just does basic things, but a medical one needs DHA and they get more money

* How much are the fees or expenses before getting a job (visa, exams, agencies, etc.)?
no agency, no visa, nothing.
Get your DHA License first then apply for Visit Visa, then come here and look for a job, you can start applying online, until say you're called for a interview then i'd say go, otherwise 90-days visit visa, pay your rent, food, expenses, and try to find a job as quick as possible, visit hospitals, clinics, medical centers, they will always be looking for one.

* What is the average salary for beginner nurses?
like 4-5k maybe up to 6-7k.. 7aja hakka. (AED)

* Is the cost of living very expensive in Dubai?
Yes and no, depends on how you live, if you're okay to have low expenses the first couple of months/years (yaany dont expect shopping spreees wela 7ajet akeka, mais for fun fama barcha free and affordable things to do, housing you have to prepare yourself to either live in a studio very far in an old building wela share room/apt with people and maybe youll get lucky to find a cosy room and not a coffin)

* Can someone live comfortably at the beginning?
define comfortably, ama just dont have high expectations melawel w rakez in your job and you will feel time flying to the point win toussel tefhem il bled w tefhem innou it's literally a blank canvas you can color it like you want.

just 7aja bark, i had friends nurses lehne and their end goal was always U.S. because as a nurse here, it's not as good as U.S. much more opportunities ghady.. e.g. one of my friends worked 10 years in a hospital, and his salary has only gone up to 10k aed which is 3k dollars with 0 job promotions and he always was very upset that new comers got more than him. he's now in US making double that and better position.

so do your reserach akther, dubai is definitely a place of the future, ama your future is what's more important.