The little handheld scopes are essentially just toys. They are marginally better than no scope at all but I would not want to have to get by with one. IMO you are better off saving your money up until you can afford something like a Rigol or other budget DSO, they are larger than handheld but still quite compact. If that is really too much of a stretch then you could look for an older used scope and pick up one of those.
There is a saying that applies here "buy cheap, buy twice", I think if you buy a cheap handheld you will quickly outgrow it and decide you need something better, hence it is cheaper in the long run to spend a bit more.
It might help to know what you actually intend to accomplish with the scope though. "Measure and display waveforms on old PC boards" could mean different things. It sounds like perhaps all you want is a toy? If that's the case then sure, you will be able to see waveforms, but what's that going to do for you? You may be better off learning more about oscilloscopes, how they are used and for what applications before you spend any money. Having a scope without having a solid understanding of what to do with it is not really going to help you much, unless you just want to play around.