Maine coons are pretty usual around these parts. A pure bred cat is pretty expensive, so I'm probably looking at a mix myself, which they basically give away for free at the vetenarians expense (some shots, id marks, etc. Which amounts to about $100-200).
I have a 19 year old cat I'm currently living with, as we have an understanding of sorts. My ex wanted him originally and then decided to stick me with him. He's basically senile. He gets confused at night and cries a lot, tries to climb into the refrigerator, and can't track anything worth a damn now. It's kind of funny to watch, but I kind of feel sorry for the guy. Getting old sucks.
It's strange how your ex dumped him with you, especially being that old (I imagine them having a history?). Surely there must be more to it than that? I remember you talking about it earlier in the second diary thread when you guys broke up, but still, was your ex moving somewhere where cats aren't allowed or something? Sounds so weird to abandon a cat that old, and dump him on you. On the other hand, I'm sure you two are liking each other anyway.
My mother was a bit against the idea of getting a cat, so imagine her reaction when I, at the age of 10, took my bike to the nearest farmer and asked him if I could get a cat. I could. For free. Farmers over here are so riddened with cats that reproduce that they give them away happily. The farmer I asked had over 70 (!!!) himself, all living in his barn, but he was too lazy/busy to do anything about them and as long as they hunted their own mice in the barn he was okay with them being there. Sort of like a all-day social pest control. Of course, I imagine him spicing the story a bit since I was a kid and he was a farmer, so he probably fed them once in a while and enjoyed their company. Either way, point of this anecdote was that my mother had to live with the cat since I was at school and my stepfather at work, so they developed a closer relationship than my mother wanted to admit. Your "understanding" with this old cat gives me that same vibe.
Purebreds are so darned expensive around here (I saw a Sphynx cat looking a for a replacement home, going for $3000. It must be a competing cat, but it gives you an idea what numbers we're looking at for pure breds. A normal pure bred goes for around $1000-1500. That's too much, imo. Divide that number by 10, and I'll take it. Point being that since the pures are expensive, I'll most likely take a mix, and since I like bigger cats, a maine coon/norwegian mix is very attractive - just like Idsynchrono up above there.