I got burned by buying a busted LQ9 back in 2014 or so. Plan was to put in in my 99 Silverado. The front main bearing had spun. I half-tore into it and stayed like that until last summer. By then water had gotten into it. I did finally get it disassembled, after struggling with seized stuff. The first 2 mains seem the worse, but the cam, rod and remainder of the main bearings actually looked okay.
Decided against rebuilding for the time being because I don't really have the knowledge, money, and time effort. A local place quoted me like $1,600 for a complete rebuild. I had bought a book on rebuilding LS engines too. But it does get expensive quickly. Bearings, complete gasket set, and misc. items add up. Don't even get into rotating assemblies, forged stuff, etc. Sadly, the engine block is in my backyard with a plastic bag, probably getting wet.
My buddy kept trying to persuade me to rebuild it, as those engines are pretty popular. But the only way I can think of doing it on a budget is to get ahold of precision measuring instruments that I don't own and take my own measurements and see what it really needs to be done; basically, be my own machinist. At the bare minimum probably needs align (line?) boring, crankshaft grinding, and I don't know what else...
Maybe I'll rebuild it at some time down the road, but in the meantime I got a complete, working 5.3 for my swap for a whopping $400.