Possible downfalls of a cheaper scope such as the ones from harbor freight:
1. low resolution
2. too big to fit in a spark plug hole
3. no light
4. no articulation
I don't have any personal experience with these scopes, but you really need to think about what you're going to use it for and whether these will be able to do the job. The main purpose I would have for such a tool is to look into piston cylinders or maybe inside the engine case of a 911.
So you need something that has those features I mentioned above. If you get the scope in the cylinder but can't discern cross hatching because the resolution is too low, then what good is that? That also will mean you might not be able to see scratches in the wall.
If you have no light and try to improvise with a flash light, you are still going to get much more limited visual information as compared to a scope that has a built in lamp
an articulating tip lets you manuver in tight spaces and if in a cylinder, might be able to turn it so that you can get a look at the valves.
Hawkeye Borescope Flexible kits by Gradient Lens Corporation
Just a few things to think about.