Questions about underground fighting / backyard fighting

I've been propositioned lately to fight in some underground / backyard fight. I declined at first, but there will be a 20' ring, headgear, and gloves. The fighter who lands the most blows takes home $1,000 cash.

Now I have no formal training. Minimal sparring / heavy bag / speed bag training as a kid with my dad. I've always done a little shadow boxing here and there for cardio. Any tips on what to do here? It's a little hard to pass up the opportunity for that much cash.

I'm 5'11. 213 lbs. At about 20-25% bf.

My opponent is claimed to be 5'10. 235 lbs. And 31% bf. He has no fights / formal training. Just 'goofing around with friends' as he put it.

I've been lurking here for a while and want to get into amateur boxing anyway within the next year. What's the verdict, here?

Update: The organizer backed out and says that some people involved were arrested and that he was reprimanded by the sheriff's office. I think he was full of shit the whole time because this all fell through after I said I'll need safeguards to be sure that I got the money in the end. I wanted to see it, and he bitched out.