Well, I've owned/shot/hunted with several, over the last 35 years - along with 7 other hunters in my annual Maine deer hunting party.
There are TWO different Ruger .44 Auto Carbines - the older, tube magazine model in the ad you posted, made from 1961-85 (early versions were named "Deerstalkers"); and a rotary-magazine Mini-14 on steriods .44 Auto Carbine called the Model 99/44 Deerfield.
Although I've had both types, I much prefer the original/older model - BUT there's a few things to be aware of.
1) They were designed around factory 240gr JSP/JHP ammo, and do their best with equivalent ammo - lead boolits will clog the gas system shortly, jamming the rifle and leading to a daily PITA teardown/cleaning.
2) Parts/Service are hard to find - with some parts, like the trigger housing, unobtainium.
ALWAYS physically pre-check a potential purchase for a cracked/broken trigger housing prior to purchase, since a bad one is a deal-breaker IMHO.
If the stock cannot be removed for the inspection, a check can be preformed with the action in the stock anyway.
With a finger inside the magazine throat, and the thumb of the same hand outside the bottom metal, grab the barrel/receiver firmly and attempt to move the front of the trigger housing up/down in relation to the receiver.
ANY movement means that the trigger housing front attachment lip(s) are either cracked or broken - they are non-weldable/non-repairable.
If the finish is hardly worn off the bottom feed latch, which gets pressed by ammo noses when loading, it would indicate to me that the rifle's not been fired very much, no matter what the outside finish looks like.
Wood refinishing's a no-brainer.
They shoot sweet - I usually buy whatever commercial .44 Mag ammo's "on sale" - with this as an average 100yd group:
(the target rings are 1" apart)
This is my current carbine:
.