That Beseler 67 Dichro - not bad IF it had the dual column (as some versions had) but not with that wimpy single column. The Omega B-600 - you'll outgrow it quickly. Take it if it's given too you, but don't spend much money at all on it. I'd avoid Dursts unless they have everything you need; accessories hard to find on this side of the Atlantic.
If you haven't already, research a bit on using Dichro heads vs. filters for variable contrast. Both will work, but Dichro heads easier. OTOH, they add complexity.
One of my medium format favorites are a Beseler 23 CII or C III. A bit like the proverbial VW of enlargers. Not fancy but they work and accessories easy to find. I'm using one with a dichro head until I fix my overly fancy Omega D5500. I would not pay more than $90 for the condenser head version or $150 for one with the most recent dichro head (looks like
this). More if it comes with good lenses and/or multiple neg carriers.
One quirk with the Beseler 67 and some more recent Omegas is the you might see the same head with different size columns. Two (columns) is generally better than one and thick/substantial better than thin/wimpy. The classic Omegas are a bit of an exception to the 2 vs 1 column, but they're substantial, 1 column designs.
If you're looking in Atlanta, might be best to take your time and wait for something good. It's always good to download and read the manual first so you can spot if something is missing. A short bit of time with a mouse found this:
https://www.facebook.com/groups/AtlantaFilmPhotographers/ Might be a good place to start your search.
If buying a dichro enlarger, test to make sure all 3 filters are working properly. You can hold a sheet of white paper under the lens to check.
As to ventilation, I have a small darkroom and, with standard chemicals, don't bother with ventilation. Maybe if I was in there for hours at a time without opening the door I would.