Possibly. I have the Nikon D5200 and you can find those for good prices with a lens or two.
As for correct lens for aquarium photography, there is no single good lens. Depending on what you are trying to photograph, the lens will change. Any lens that promises to be good at many different things is typically junk. So, if you are looking to do close up shots of coral or fish, you will want a macro lens, specifically something around 75-100mm. This gives the reach while still producing tight close ups with good detail. The Tamron 90mm macro lens is a good macro lens that I see a lot of people using. If you want to take wide angle tank shots, then you will need a lens with a very short focal length, something <20mm.
Don't skimp on lenses. The camera body is important, but the lens is what dictates image quality. You can't fix focus or aberrations easily, but you can adjust exposure, noise, and contrast in photoshop.
I use eBay for the most part in my camera purchases. I've purchased everything from my Nikon D5200, D7100, and D810 to even the massive Nikkor 300mm f2.8 lens off eBay. All used and in great shape. Heck, the 300mm was shipped from Japan and was in the best shape of any purchase I've made. A good rule of thumb to follow, if the seller doesn't or won't show close ups of the lens elements, then don't buy it.