I too have a small laser from Universal Laser Systems in AZ
30W 12x16 table. I found it locally on eBay in excellent condition for $2500
I use Corel Draw which is about $100 software (I use it simply because I was familiar with it)

ULS and Epilog (and I believe Trotec) are all air cooled lasers; no water cooling needed.
They are considered some of the best lasers for sale today (my old employer used all Epilog and they are 10 years old and working fine)

No matter what laser you purchase you will definitely need a proper exhaust setup.
Apart from health issues, you can damage your lenses due to inadequate exhausting (although adding air assist to the lens can help with that as well)

There are a few websites that specialize in used lasers as well as many online forums