Im lost here now.
You want to get into squats and drug den etc where you know its really filthy with pigeon stuff and body fluids and you looking at a wet/dry vac.
That is no where near a carpet cleaning machine - it just sucks either dry or wet debris.
Are there carpets to clean?
Or is it just general cleaning you looking to do.?
You did mention carpet cleaning in your first post so I have assumed carpet cleaning is needed.
If so, and the places are really bad like you say, then you need to be spending thousands on a carpet cleaning machine, together with relevant cleaning fluids.
Contract it out - sounds like you havnt got the money to invest.