I'd say look for a decent deal on a solid used boat from one of the premium manufacturers. treat it well while you own it, and you'll probably get close to what you paid for it in the event that you sell it after a year. If you're looking to get on the river as cheaply as possible, this is a far better option than buying a piece of junk near the end of its life. You'll end up spending more time on the river with a safe boat, and less time sniffing glue.
There is a learning curve to raft repair, it is time-consuming and can be expensive, and you need a good place to do the work. I've gone both routes and wasted about $500 on my first raft because I wanted to be on the river "cheap".