Questions on buying a used Lexus RX 350
 

I'm looking to buy a luxury SUV that's used and has already depreciated away most of its value (why buy a low level trim 1-2 year old Toyota when I can get a much nicer 6-8 year old Lexus for the same price? ). I realize this is risky with many vehicles, but Lexus has a reputation for extreme reliability and low maintenance costs, which is why I'm leaning towards Lexus over brands like Acura, Volvo, and especially the German cars. I only drive about 10k miles per year.

It appears the Lexus RX 350 was redesigned in 2010, and from then, underwent only very minor changes until 2016 when it was redesigned again. I'm looking to keep my purchase under $20k and buy something that's depreciated most of its value already, so year 2015+ models are out for me. Is it worth it to just get a 2010 or 2011 Lexus RX 350? Browsing through used car listings, there seem to be a ton of them under $20k, some even under $17k. Do I need to worry about nightmare maintenance issues even if the vehicle has 90k miles on it, as long as I make sure it's properly inspected before I purchase?

Is there really anything in the 2011, 2012, 2013, or 2014 RX 350 models that makes them worth considering over the 2010? I don't care about the sportier grill on the 2013, the 2012 engine which operates at 87 octane fuel is a nice upgrade but I'd rather save a few grand by getting a 2010 or 2011. I don't care about a power lift gate either.

I know I want a backup camera, but it appears most of the 2010 and 2011 models have them, even if it wasn't standard in those years.

Are there any optional features on the 2010 or 2011 models that would be recommended, or features on the 2012 or 2013 models that might be worth looking at? I'm not sure what all the optional features are.

The engine in the 2010 is a variant of a transverse-mounted type(2GR-FE) used in 5 different Toyota models. I believe the 2010 Lexus motor may actually be a longitudinal engine and I am fairly sure it was the 2007 that had this north-south engine. May be mistaken about the year.
The Toyota versions are known for premature water pump failures, early issues with COP(coil-on-plug) codes and worst of all, VVT-I hoses bursting - good-bye engine.
Quite frankly I do not know if these problems found their way to their Lexus cousin - RX350.
There are a number of Lexus forums. You may have been there already. If not, join a few and dig around.
Go to Toyota's web site - there is a section in the upper right called "Owners". You join - specify a username/pswd - then key in the specifics, one being the VIN. You will be able to see all dealer service done on that car. I'd bet a buck Lexus offers this at their web site. Before you buy, go there and provide VIN/etc and see what Lexus dealer(s) have done.
Some Toyota owners DIY; I suspect Lexus owners are less inclined. This might give you an idea of maint. warranty, T-SB - trouble service bulletin work performed on the vehicle.

I never want a timing belt motor,had two both slipped time.

Neither do I. The Lexus RX350 has a timing chain.

Toyota started moving away from tbelts on many of their engines in 2005.
The older 4 bangers for the most part have a belt, although my '83 PU had a chain. The 4.x V8 in the Tundra has a belt. The 5.7 has a chain.

But...no belt on the RX350 in question here.

The RX300s would crack the heads or block bad enough to pour coolant out the exhaust too.