Need Info on Working Visa process (Budapest)

Hi,
I'm moving to Budapest soon to work (from Non-EU country). I already have a job offer and I have got a "D" type working Visa.

Now agency that is handling my immigration is telling me that once I get to Budapest,
- I will 1st have to find an apartment to rent,
- then based on that address, apply for a residence permit and social security.

I can join work only once all this is done.

Is this true? It sounds quite not right that even after getting a work Visa, these process can't move in parallel to a person working.

If yes, how long does this process take after I have finalized an apartment?