That is a wide open question. The worst units are really good. Ice fishing is a different game since most equipment works best while moving.

Just as a data point, I have a Lowrance 520C. It is 16 years old. I can easily see a crappie jig in 25ft of water and find a brush pile or drop off just as deep with it. Though many improvements have been made since it came out, the difference between it and the new units as far as seeing things under your boat and marking them is trivial. I’ve used that little 5” display to put a lot of fish in the freezer.

My advice is to get something cheap enough you can put a unit at the console and the bow that share waypoints so you can idle around and find spots, then get back to them on the trolling motor. That will get you 99% of what any unit does regardless of price.