Welcome to the site.
Before purchasing, make sure you study up on the problems that plague some of the early second generation Avalanche owners.
Primarily engine problems with the AFM or Active Fuel Management system, also known as DOD or Displacement on Demand, that was introduced in 2007.
This site and the Internet are full of discussions of the issues people have had and are having with the AFM system in mostly 2007 and 2008 models.
For the most part, it would appear that 2009 to 2013 models seem to have fewer problems as GM may have corrected some of the shortcomings of that system.
The more drastic method to remedy the problems of this system appear to be the replacement of the cam, lifters and other AFM related engine parts and the tuning out of the AFM commands in the computer.
For me, that would be enough for me to look for a later model truck, unless I found a older truck that checked all of the boxes and I was willing to invest the time and money to fix the engine.
But, then again, there have been owners of those two models that report having no issues at all.
Yet.
Best of luck finding the truck that meets your needs.