Target the ResMed or Respironics brand auto/apap model machines.
cpap.com is an excellent source to buy from.
These would be the machines I would recommend or get if I were in your shoes.
ResMed AirSense 10 AutoSet $883https://www.cpap.com/productpage/resmed ... idair.html
Respironics DreamStation Auto CPAP with humidifier and heated hose $866 https://www.cpap.com/productpage/pr-dre ... chine.html
Of the 2....I would lean towards the ResMed (and I have owned both brands) because we don't know what pressures you are going to end up needing and if you need pressures that are higher I think that ResMed exhale relief is probably a little better at the higher pressures.
Both are excellent machines but the ResMed has a few more pros to it IMHO. Prices are very close unless you shop around and want to save some money and get a prior discontinued model.
You might check secondwindcpap.com
they offer some gently used machines as well as some new open box specials. They are good people too.
Just make sure that you know your models and which one does what and don't get fixated on price.
Amazon is also a viable choice....just make sure you know the model you are looking at.