Annual fee after first year, major value is in travel rewards that require reasonably high spend, there are other cards etc.
Is it %100 necassary to have a 5k CL in order to get that card?
No. My sister had a Chase Freedom for about one year and was able to get approved for the Chase Sapphire Preferred with no other limits at 5000. Since you have a Chase Freedom, you stand a better chance at getting approved for the Chase Sapphire Preferred.
What is it?
In most cases, a CL of $5K or greater on a single card, not total. The idea is that this shows you have experience to handle that size CL.
Read some posts here and there, but I'm going to drop my own opinion. I recently acquired the CSP, but this was after I did hours upon hours, weeks of research. This isn't something you should jump into, especially when you look at the daunting AF after the first year.
You don't have to be making a lot of money to make the CSP worth it. With that being said, I would estimate you should be making around 40-45k to make the CSP worth it to some degree. You definitely make the AF a non-factor if you combine your Freedom card with your CSP. Take this piece of anecdotal evidence.
I worked in retail last year due to trouble finding a job. I got the Freedom Card and accumulated about 16,000 points not counting the initial bonus. This was from bills, small purchases (10 + 10) and using the 5% bonus. With a 0 AF, this is a great card by itself. Thankfully, I have found a more career oriented job, and because of my salary I decided to get the CSP as my "travel" card. Now with my salary, by itself it is a dud. However, if my sole focus is to combine my freedom points with CSP points for travel, then it becomes valuable. I compared this tag team to some other solo cards like Capital One Venture Rewards and BoA Travel Rewards. Based on my spending, the tag team of Chase was better for me.
So all in all, just make sure you do the math, and see if CSP will really benefit you.
Finally, I didn't have a CC with 5,000 before applying for the CSP. But I do have a long history with Chase (7 years).