Honestly for 5k; you're probably looking at something like a 90's bass boat with a 75hp Mercury 2-stroke.
Now, you'll not hear me talk bad about 2-stroke engines; the vast amount of boat fishing I've done was on a 2-stroke. A well-taken care of, maintained two-stroke can run. But an old 2-stroke engine with plenty of hours on it can have a myriad of issues. Not to mention the fiberglass boat attached to it; which can have holes, transom issues.
I'm not saying you can't find a sweetheart of a deal. But if you plan to spend 5k on a bass boat, be prepared to spend a lot more money on it that you didn't see coming. Now, you can get a new Bass Tracker Classic XL with a 5 year warranty, decked out with modern equipment and a 4-stroke engine that is easier to maintain and gets better gas mileage, a 16' that you can work in shallow water. Now it's around 15-17k new for one, and occassionally you can find them a couple years old on marketplaces in the 8-10k range.
This being your first bass boat, lets be real; you're learning how to use your equipment. Aluminum boats can take a bit more punishment than fiberglass boats, and they don't cost a zillion dollars. They are light and can tow well. You'll be able to fish in places a 21' fiberglass bass boat dare not go to.
I'm looking at a boat of my own. Personally, I'm going with a Tracker 175, which is a foot longer and a foot wider than the Classic XL. It's also got a bigger motor, and they go new for about 23k.
Take your five grand, put it toward a Bass Tracker (New or gently used), finance the rest for a relatively low monthly payment, go fishing, and if you need something fixed, utilize the warranty and make it someone else's problem.
Otherwise, if five is all you're gonna spend, take a guy that knows boats with you, pay him a c-note to check out the boat for you and have him tell you if it's worth buying or not.
Hope this helps.