Not sure if I already asked about this but is the inversion completely necessary here?
Short answer: yes. Longer answer: The V2 rule is very firm. Once you start a sentence (that is not a question or a subclause) with an adverbial, the verb needs to go right after that.
Regarding "hos mig", does it actually mean " my house/place"? I've seen texts where the clause was "hemma hos mig", wondering whether that makes a difference
The English here seems grammatically incorrect. At least I would not say it as a Canadian English native speaker. It needs to be "Tonight I WILL sleep at your place." or "Tonight I AM sleeping at your place." "I sleep at your place" means that happens habitually, not just once. Adding tonight just makes it awkward.
I agree that it's awkward but I don't think it's grammatically wrong. "Tonight, we dine in hell!" comes to mind as another example of the same sort of strange grammar.
Why is 'I natt' used as tonight as it directly translates to 'in the night', and we have 'ikväll' to use as tonight do we not?
i natt means this night. In Swedish, kväll is evening and natt is the 'real' night, but in English they seem to use night to cover both, which causes some confusion.
PS so i kväll means 'this evening' (of course 'tonight' is also used in this sense) and 'in the night' would be på natten.
i could understand, based on one of below comments why the verb came before the subject. but i still dont understand why it is '' hos er'' rather than '' er hos'' as we normally use.. am i missing something here
I think you miss the meaning of "hos" :). It is a preposition and means "at someone's".
Why is "Tonight I sleep with you" wrong? Is it just because "hos er" is a fixed phrase?
From another site: "The Northern Germanic languages all share a handy preposition meaning something like ‘at the home/place of’. In Swedish, this preposition is hos, pronounced [hʊs]."
Plus, in English, "I sleep with you" takes on an entirely different meaning.