I'm trying to get into deep dropshotting this summer and have come to realize that i will do much better if i can get a sonar system. I dont own a bass boat but do have a rowboat with a trowling motor which i want to hook a fishfinder up to. What's the best bang for my buck?

As long as it is a Garmin !

I usually prefer the detail that Lowrance gives, but they are a little more pricey on their basic units.  Would probably just do a standard stern mount off of the back and put your screen where ever you can see it while trolling.