Kinda hard to answer the question without knowing the condition of the truck and capabilities of the OP.
A few examples and personal experiences:
One of my kids' classmates' dad has on 03 Tahoe with the 4.8. We know the family for years now. He's got nearly 400k on it. He did tell me it will burn a bit of oil if he uses it for heavy towing. I've seen the truck on the carpool lane and it's freaking clean! He's taken good care of it, and it shows. Transmission was rebuilt once. We were talking recently and he said he's interested in getting his engine overhauled.
Another former co-worker had a Tahoe, also 03 with the 4.8. He passed it on to his DIL and it had close to 400k. They eventually divorced and the girl kept it. Last he heard she was still driving it, over 400k. Original transmission on that one! Unbelievable!
My buddy has 01 Silverado RCSB 4.3 he bought new out of HS. Over 400k. Also original engine and transmission! His brother had bought a similar truck, a 2003 model. He got hit on the bed and my buddy bought it from him and replaced the bed/axle and that one is I believe also around the 400k mark. He takes care of them. Even washes/waxes them weekly.
My 99 Silverado made it to 260k on the original 4.3 engine. I retired it because I needed more space for dropping my kids off school. The engine had developed low oil pressure. I considered selling it for cheap. Truck was in very good condition otherwise. I eventually swapped a $500 5.3 and it's a reliable truck again. I've put about 12k since the swap. I've actually gotten offers from guys asking if I want to sell it when I wash it and put shiny stuff on the tires.
I just finished reinstalling the engine on my 06 Suburban daily driver. It had an intermittent lifter tick at 262k that was bugging me. $1400 or so for a basic refreshing: piston rings, bearings, gaskets, etc. It was my first engine overhaul. I hope to get another 100,000 miles+.
So, these vehicles are definitely capable of staying on the road for a long time and very economical to repair.