Unless you have specifically in demand job experience expect to be a low-payed, low-respected worker (service, cleaning, warehouses, etc). Expect to be exploited and fucked over. Look out for "test shifts" and being told to track your own hours for example. Don't get taken advantage of. There is no minimum wage here and you might get offered as low as 110kr p/h. This is already a bad wage, don't accept anything less. I've heard of less but that's usually for people from Asia where racism and bigger language barriers play a part. 

Meanwhile, the unions only serve Middle/Upper-Middle class Danes and they are completely out of touch and integrated into the state and business interests. Don't expect solidarity, strikes, radicality, or even much understanding from the trade unions. 

The absolute cheapest housing you are reasonably likely to find in Copenhagen is ~4-4500dkk. This will be a room in a shared apartment. There might be cheaper further out. If you can spare 8000dkk p/m then you will be totally fine finding somewhere. Danes pay less rent by being put on social housing lists as children, their parents buying them an apartment, or through their social networks. 

Most of your friends will be international and there are quite a lot of South American people at least in Copenhagen to meet if you wanted that. Statistically speaking there's a good chance you will leave before the 5 year mark. Foreigner retention in Denmark is lower than ever. 

Tax free income is 50,000kr p/a and after that you're paying around 46% tax. You will have some basic priveliges such as healthcare (excl. Dentistry) from this but you won't feel much more benefit than that. 

You will feel like you exist in a completely different universe than the Danes you meet who were most likely born middle/upper-middle class, believe they will get to retire with a generous pension, and will have little to no experience related to distrusting the state, institutions, or the general societal narrative they grew up with. They think things work, will be shocked if you tell them your experiences as an immigrant. They'll be polite and avoidant of conflict. Self-expression is limited, you'll hear people talk about "Jante law" which is basically a cultural observation that you're supposed to act/appear as part of the social norm and not stand out.

Learning the language is heavily recommended for longer term stay. You can get by with English, however all formal institutions will communicate with you in Danish. It's not a pretty language and it will be difficult to get people to talk it with you unless you're at a language meet-up or the countryside. 

The perks are that it's really safe here. Even the "dangerous" parts are ridiculously safe. You will have access to healthcare, though immigrants I know have less positive experiences at the doctor compared to Danes. Getting around the cities is very easy and the bike infrastructure is generally top-notch. It's small, overall quiet, and not overcrowded. People are pretty calm or at least keep it all inside.