Well I'm just putting out feelers at the moment, I'm not about to go out & spend 1000s immediately : )
Since you want to print so large, even a used printer is going to be expensive. I picked up a used Epson 4800 for $500, but the bigger ones are still a few k used. You'll need one that is 44" wide and that is hard to come by. I think the Espon 9700 is your best bet for finding a good deal on a used model that meets your reqs, however it is not the greatest printer. The 9890 or 9900 are far superior.
All this being said, unless you will be printing A LOT, you are better off just going to a lab. Even if you can find a deal on a used printer, 350ml ink cartridges for the 9700 are $150 a piece, and the printer takes 5 (another reason maybe to look for a 9890, but then you have to buy 9 cartridges), not to mention 44" inkjet canvas rolls are really expensive too. A 30x40 print on canvas will be a few hundred dollars at a lab, but depending on how many prints you will need during the lifetime of the printer, you might actually save money by letting someone else do it.