The people knocking private bots either have a dog in the fight, or aren't as informed as they're pretending. I've coded well over a thousand bots in the last 10+ years, and I've never charged any client for updates. If they later want new features, then possibly yeah. But for fixes, and the like - no. Plus, I've seen a lot of public bots on these forums that _do_ cost money for updates (as well as for additional licenses, and other things like addons), so it's a moot point either way. Additionally, just like there are benefits to public bots - there are also benefits to private bots. A good analogy is multiplayer cheats - for any given game, look how quickly the public ones are patched - meanwhile, I still have private exploits for the UT99 engine that I came up with 9 years ago. Had they been released publicly, they'd have long ago been fixed. Another major benefit to private bots vs public is that you typically get the complete source, can make any changes you desire, and can rest assured knowing that the chance of it being malicious (vs, say a public bot) is pretty much nonexistent. Whereas with public bots, look at them. All the ones I've seen are packed, and worse, they're self-modifying - which is the same exact behavior as a lot of malicious software.
OP: If you're still looking, I'm interested. I'd be curious to know your budget prior to beginning any work though. If you're interested or have any questions, let me know and I'll PM you my contact information and then we can go from there.