IMO, from experience, a kart that “needs work” is generally more trouble than it’s worth.
As easy as it is to work on these karts, the reality is most of the “work” involved consists of pulling out your wallet and buying the replacement parts – and while not necessarily “expensive”, a lot of the time, you’ll find it would be just as cost effective to have spent a few hundred more up-front on a kart that doesn’t “need work”.
The other benefit is that rather than getting a well-used frame with that kart that “needs work”, you’ll likely be getting a lightly used frame by going with a kart that doesn’t need work. And the kart that doesn’t need work will likely be much more competitive.
The only possible exception might be the case where the kart that needs work is coming with a lot of extras that are transferable to other karts or just generally needed to race (kart stand, rims, hubs, Mychron, transponder, sprockets, tire tools, etc), where you’re really just paying for those extras and the seller is throwing in the kart just to get it out of his garage. But you’d better realize in that case that you’ll still need to spend more to get that older kart on the track, and it still likely won’t be competitive.